CHAPTER IX

THE ORDER UNGULATA

Under this term may be included provisionally a large and rather heterogeneous group of mammals, the existing members of which form the Pecora and Belluæ of Linnæus, the Ruminantia and Pachydermata of Cuvier. A few years ago it was found convenient to restrict the order to a well-marked and distinctly circumscribed group, comprising the two sections known as Perissodactyla and Artiodactyla, and to leave out such isolated forms as the Elephant and Hyrax; but the discovery of a vast number of extinct species, which could not be brought under the definition of either perissodactyle or artiodactyle Ungulates, and yet are evidently allied to both, and to a certain extent bridge over the interval between these and the isolated groups just mentioned, makes it necessary either to introduce a number of new and ill-defined ordinal divisions, or to widen the scope of the original order so as to embrace them all.

The existing forms are all animals eminently adapted for a terrestrial life, and in the main for a vegetable diet. Though a few are more or less omnivorous, and may under some circumstances kill living creatures smaller and weaker than themselves for food, none are distinctly and habitually predaceous. Their teeth are markedly heterodont and diphyodont,—the milk set being well developed and not completely changed until the animal attains its full stature. The molars have broad crowns with tuberculated or ridged surfaces. There are no clavicles.[173] Their toes are provided with blunt, broad nails, or in the majority of cases with hoofs, more or less enclosing the ungual phalanges. The scaphoid and lunar bones of the carpus are always distinct. The humerus has no entepicondylar foramen. The number of digits varies from five to one; and the radius and ulna may be united together.

The more generalised of the fossil forms do not conform in all respects to the above-mentioned characters; clavicles being present in _Typotherium_, and perhaps in some of the Condylarthra, while in the latter group the humerus may have an entepicondylar foramen, and thus approximate to the corresponding bone of the Carnivora. Wide as is the gap between existing Carnivores and Ungulates, there are indeed more or less strongly marked evidences of affinity between the earlier members of the two orders, as will be again noticed under the head of the suborder Condylarthra. A departure from the normal type of foot-structure is exhibited by the extinct _Macrotherium_, provisionally included in the Perissodactyla, where the digits terminated in long and curved claws.

As a general rule, the cheek-teeth have distinct roots, and in those of the existing suborders a gradual increase in the height of the crowns of these teeth may be noticed in passing from the more generalised to the more specialised types. Those teeth in which the crowns are low, and their whole structure visible from the grinding surface, are termed _brachydont_ (Fig. 122); while those with higher crowns, in which the bases of the infoldings of enamel are invisible from the grinding surface, are known as _hypsodont_ (Fig. 123). Again, when the tubercles on the crowns of the molars are more or less cone-like in form the tooth is said to be _bunodont_; but when they are expanded in an antero-posterior direction and curved into a crescent shape the tooth is described as _selenodont_.

[Illustration: FIG. 98.—Right fore foot of Indian Elephant. × ⅛. U, ulna; R, radius; _c_, cuneiform; _l_, lunar; _sc_, scaphoid; _u_, unciform; _m_, magnum; _td_, trapezoid; _tm_, trapezium; I to V, first to fifth digit.]

The whole order may be divided into the Ungulata Vera, containing the suborders Perissodactyla and Artiodactyla, and a somewhat heterogeneous assemblage of animals which may be called Subungulata or Ungulata Polydactyla. Cope has pointed out a character in the structure of the carpus by which the latter are differentiated from the former. Thus in all the Subungulata the bones of the proximal and distal row retain the primitive or more typical relation to each other (see Fig. 98); the os magnum of the second row articulating mainly with the lunar of the first, or with the cuneiform, but not with the scaphoid. But in the group to which the vast majority of modern Ungulates belong the second or distal row has been shifted altogether towards the inner side of the limb (see Fig. 99), so that the magnum is brought considerably into relation with the scaphoid, and is entirely removed from the cuneiform, as in the great majority of existing mammals.

It will be on the whole more convenient to commence our survey of the members of this suborder with the more specialised group of the Ungulata Vera, in which the Artiodactyla will be taken first.

UNGULATA VERA.[174]

In the typical Ungulata the feet are never plantigrade, and the functional toes do not exceed four—the inner digit being suppressed, at all events in all forms which have existed since the Upper Eocene period.[175] The os magnum of the carpus articulates freely with the scaphoid. The allantois is largely developed, and the placenta, so far as is known, is non-deciduate; the chorionic villi being either evenly diffused or collected in groups or cotyledons (in Pecora). The testes descend into a scrotum. There is never an os penis. The uterus is bicornuate. The mammæ are usually few and inguinal, or may be numerous and abdominal (as in Suina), but are never solely pectoral. The cerebral hemispheres in existing Ungulates are well convoluted.

The group is now, and has been throughout almost the whole of the Tertiary period, composed of two perfectly distinct sections, differing from each other, not only in the obvious characters of the structure of the limbs, but in so many other parts of their organisation that they must be considered as of the rank at least of suborders. The characters of these divisions, first indicated by Cuvier, were thoroughly established by Owen, by whom the names whereby they are now generally known were proposed.

_Suborder_ ARTIODACTYLA.

This is a well-defined group, traceable from the Eocene period, though then apparently by no means so numerous as the Perissodactyles. Some of its types, as that represented in the existing Swine, have retained to the present time much of the primitive character of the group; but others have been gradually becoming more specialised and perfected in structure, and its latest modification, the Cavicorn Ruminants or _Bovidæ_ (Antelopes, Sheep, and Oxen), are now the dominating members of the great Ungulate order, widespread in geographical range, rich in generic and specific variation, and numerous in individuals—forming in all these respects a great contrast to such decadent types as those represented by the Tapirs and Rhinoceroses.

[Illustration: FIG. 99.—Bones of right fore foot of existing Artiodactyles. A, Pig (_Sus scrofa_), × ⅓; B, Red Deer (_Cervus elaphus_), × ⅐; C, Camel (_Camelus bactrianus_), × ⅛. _U_, Ulna; _R_, radius; _c_, cuneiform; _l_, lunar; _s_, scaphoid; _u_, unciform; _m_, magnum; _td_, trapezoid; _tm_, trapezium. From Flower’s _Osteology of Mammalia_.]

The principal anatomical characters by which the Artiodactyles are distinguished from the Perissodactyles are as follows. The premolar and molar teeth usually not alike, the former being single and the latter two-lobed. The last lower molar of both first and second dentition almost invariably three-lobed; and the first tooth of the upper cheek series always without a milk-predecessor. Nasal bones not expanded posteriorly. No alisphenoid canal. Dorsal and lumbar vertebræ together always nineteen, though the former may vary from twelve to fifteen. Femur without third trochanter. Third and fourth digits of both feet almost equally developed, and their ungual phalanges flattened on their inner or contiguous surfaces, so that each is not symmetrical in itself, but when the two are placed together they form a figure symmetrically disposed to a line drawn between them. Or, in other words, the axis or median line of the whole foot is a line drawn between the third and fourth digits, while in the Perissodactyles it is a line drawn down the centre of the third digit. Distal articular surface of the astragalus divided into two nearly equal facets, one for the navicular and the other for the cuboid bone. The calcaneum with an articular facet for the lower end of the fibula. Stomach almost always more or less complex. Colon convoluted. Cæcum small. Placenta diffused or cotyledonary. Mammæ few and inguinal, or numerous and abdominal.

In treating of many sections of mammals, it is only from the existing species that our characters and classification can be derived, and to these chiefly our observations upon the group must be directed, many of the extinct forms being so little known that they can only be referred to incidentally. With the Ungulata, however, it is quite otherwise. The history of the Artiodactyla throughout the Tertiary period is now well known, and throws great light upon the position and relations of the existing groups.

The principal modifications which have taken place in the type from its earliest known and most generalised manifestation have been the following:—

1. As regards the teeth. Assumption by the grinding surfaces of the molar teeth either of a bunodont or of a selenodont form. Modification of the latter from a brachydont to a hypsodont type. Loss of upper incisors. Development of canines into projecting tusks. Loss of anterior premolars.

2. As regards the limbs. Reduction of the ulna from a complete and distinct bone to a comparatively rudimentary state, in which it coalesces more or less firmly with the radius. Reduction of the fibula till nothing but its lower extremity remains. Reduction and final loss of external pair of digits (second and fifth), with coalescence of the metapodial bones of the two middle digits. Union of the navicular and cuboid, and sometimes the ectocuneiform, bones of the tarsus.

3. Change of form of the odontoid process of the axis vertebra from a cone to a hollow half-cylinder.

4. Development of horns or antlers on the frontal bones, and gradual complication of form of antlers.

5. By inference only, increasing complication of stomach with ruminating function superadded. Modification of placenta from simple diffused to cotyledonary form.

The primitive Artiodactyles, with the typical number (44) of incisor, canine, and molar teeth, brachydont molars, conical odontoid process, four distinct toes on each foot, with metapodium and all carpal bones distinct, no frontal appendages, and (in all probability) simple stomach and diffused placenta, were separated at a very early period into Bunodonts and Selenodonts, although there is evidence of intermediate forms showing a complete transition from the one modification to the other. These and other fossil forms so completely connect the four groups—Suina, Tylopoda, Tragulina, and Pecora—into which the existing members of the suborder have become divided, that in a general classification embracing both living and extinct forms these divisions cannot be maintained. In the present work, however, it will be convenient to retain them, mention being made of some of the chief annectant forms in separate sections.

SUINA.

The existing members of this group are characterised by their bunodont molars, and the absence of a complete fusion of the third and fourth metapodials to form a “cannon-bone.” The full Eutherian dentition is very frequently present.

Remains of very generalised swine-like animals have been abundantly found in Tertiary formations both in America and Europe. In the former continent they never (so far as present evidence indicates) underwent any great diversity of modification, but gradually dwindled away and almost died out, being only represented in the actual fauna by the two closely allied species of Peccary, among the smallest and most insignificant members of the group, which have existed almost unchanged since the Miocene age at least, if the evidence of teeth alone can be trusted. In the Old World, on the other hand, the swine have played a more important part in recent times, having become widely distributed, and throwing off some curiously specialised forms. At the present time, though not very numerous in species, they range through the greater part of the Old World, except within or near the Arctic Circle, although, in common with all the other members of the great Ungulate order, they were completely absent from the whole of the Australian region, until introduced by man in very recent times.

The existing swine-like animals may be divided naturally into three families:—I. _Hippopotamidæ_; II. _Suidæ_, or true Pigs; III. _Dicotylidæ_, or Peccaries.[176]

_Family_ HIPPOPOTAMIDÆ.

[Illustration: FIG. 100.—Grinding surface of a worn molar of _Hippopotamus amphibius_. (From Owen.)]

Muzzle very broad and rounded. Feet short and broad, having four subequal toes, with short rounded hoofs, all reaching the ground in walking. Incisors not rooted, but continuously growing; those of the upper jaw curved and directed downwards; those of the lower straight and procumbent. Canines very large, curved, continuously growing; those of the upper jaw directed downwards. Stomach complex. No cæcum.

_Hippopotamus._[177]—This genus may be taken to include all the known members of the family; it appears to have been always confined to the Old World. The dentition may be expressed by the formula _i_ ²⁻³⁄₁₋₃, _c_ ¹⁄₁, _p_ ⁴⁄₄, _m_ ³⁄₃. The crowns of the molars (Fig. 100) when worn present trefoil-shaped surfaces of dentine; and those of the premolars are sharp. The facial portion of the skull is much elongated, the orbits are tubular and very prominent, and the mandible has a large rounded descending flange at its angle. The ears are small, the tail is short, and the legs are likewise so short that the belly is raised but a little distance above the ground. The brain is not richly convoluted, and differs very considerably from that of the Pigs, approximating in some respects to that of the Camel and Giraffe, but on the whole standing very much by itself. The stomach of the common species is of enormous dimensions, having an axial length of 11 feet, and measuring upwards of 15 feet along the greater curvature. Its axis is longitudinal, the pylorus being situated almost in the pelvis, and it is divided into three distinct compartments, of which the third is cylindrical. The liver of the adult is of extremely simple form, elongated transversely, and narrow from above downwards. With the exception of a few tufts of hair on the lips, on the sides of the head and neck, and at the extremity of the short compressed tail, the skin of the hippopotamus, some portions of which are two inches in thickness, is entirely destitute of covering.

[Illustration: FIG. 101.—The Hippopotamus (_Hippopotamus amphibius_).]

The common Hippopotamus (_H. amphibius_), widely distributed in the rivers and lakes of the African continent, is a huge bulky animal, characterised by having only two incisors on either side of each jaw; the central lower pair being very much larger than the outer ones. A male from the Upper Nile which lived for nearly thirty years in the gardens of the Zoological Society of London measured 12 feet along the back from the nose to the root of the tail.

The Hippopotamus lives in herds of from twenty to forty individuals on the banks and in the beds of rivers, in the neighbourhood of which it finds its food. This consists chiefly of grass and aquatic plants, of which it consumes enormous quantities, the stomach being capable of containing from 5 to 6 bushels. These animals feed principally by night, remaining in the water during the day, although in districts where they are undisturbed by man they are less exclusively aquatic. In such regions they put their heads boldly out of the water to blow, but when rendered suspicious by persecution, they become exceedingly cautious, only exposing their eyes and nostrils above the water, and even this they prefer doing amid the shelter of water plants. In spite of their enormous size and uncouth form, they are expert swimmers and divers, and can remain under the water from five to eight minutes. They are said to walk with considerable rapidity on the bottoms of rivers, beneath at least a foot of water. At nightfall they come on land to feed; and when, as often happens on the banks of the Nile, they reach cultivated ground, they do immense damage to growing crops, destroying by their ponderous tread even more than they devour.

A much smaller species, known as the Pigmy Hippopotamus (_H. liberiensis_), inhabits some of the rivers of Western Africa, and is characterised by having only a single pair of lower incisors. Mainly on this account, it has been proposed to regard this species as representing a distinct genus, under the name of _Chœropsis_; but since it agrees so essentially in other characters with the common form, and sometimes has two incisors on one side of the lower jaw, it appears preferable to include it in the type genus. The greater relative size of the brain-cavity as compared with the facial portion of the skull renders, indeed, the contour of the skull decidedly different from that of _H. amphibius_, but this is a feature generally found in young individuals of larger species, and also in the adults of allied smaller forms.

Both the existing species are now exclusively confined to Africa, but in the Pleistocene and Pliocene periods the genus was widely spread over the Old World. Thus in the Upper Pliocene of the Continent and the Pleistocene of England we meet with remains of a very large fossil Hippopotamus which cannot be specifically distinguished from _H. amphibius_. In the Pleistocene and Pliocene of India there are two species having three pairs of incisors in both jaws. Of these _H. palæindicus_ has the second pair in the lower jaw very minute, and evidently just about to disappear; from which we learn that it is this pair which is missing in _H. amphibius_. In the still more generalised _H. sivalensis_ the three incisors in the lower jaw are of equal size. Hexaprotodont species also occur in the Upper Tertiaries of Burma and Algeria. Small tetraprotodont species (_H. pentlandi_ and _H. minutus_) have left their remains in enormous quantities in the caves and fissures of Sicily and Malta.

_Family_ SUIDÆ.

An elongated mobile snout, with an expanded, truncated, nearly naked, flat, oval terminal surface in which the nostrils are placed. Feet narrow; four completely developed toes on each. Hoofs of the two middle toes with their contiguous surfaces flattened. The outer (second and fifth) digits of existing forms not reaching to the ground in the ordinary walking position. Teeth variable in number, owing to the suppression in some forms of an upper incisor and one or more premolars. Incisors rooted. Upper canines curving more or less outwards or upwards. Stomach simple, except for a more or less developed pouch near the cardiac orifice. A cæcum. Colon spirally coiled. Confined to the Old World.

The mandible has no descending flange at the angle. The crowns of the molars do not wear into such distinct trefoils as in the Hippopotamus, and are oblong in shape. The last molar of both the upper and lower jaw (Fig. 102) has an additional hinder lobe or talon, varying in size in the different species. The upper premolars are simpler than the true molars.

[Illustration: FIG. 102.—Grinding surface of a worn third right lower molar of the Wild Boar (_Sus scrofa_). After Owen.]

_Sus._[178]—Dentition: _i_ ³⁄₃, _c_ ¹⁄₁, _p_ ⁴⁄₄, _m_ ³⁄₃; total 44. Upper incisors diminishing rapidly in size from the first to the third. Lower incisors long, narrow, closely approximated, and almost horizontal in position, their apices inclining towards the middle line; the second slightly larger than the first, the third much smaller. Canines strongly developed and with persistent roots and partial enamel-covering, those of the upper jaw not having the usual downward direction, but curving strongly outwards, upwards, and finally inwards, while those of the lower jaw are directed upwards and outwards with a gentle backward curve, their hinder edges working and wearing against the front edges of the upper canines[179]. They appear externally to the mouth as tusks, the form of the upper lip being modified to allow of their protrusion, but are much less developed in the females than in the males. The teeth of the molar series gradually increase in size and complexity from first to last, and are arranged in contiguous series, except that the first lower premolar is separated by an interval from the second. First and second upper premolars with compressed crowns and two roots. The third and fourth have an inner lobe developed on the crown, and an additional pair of roots. The first and second true molars have quadrate crowns, with four principal obtuse conical cusps, around which numerous accessory cusps are clustered. The length of the third molar is nearly equal (antero-posteriorly) to that of the first and second together, its crown having, in addition to the four principal cusps, a large posterior talon or heel, composed of numerous clustered conical cusps, and supported by several additional roots. The lower molar teeth resemble generally those of the upper jaw, but are narrower. Milk dentition: _i_ ³⁄₃, _c_ ¹⁄₁, _m_ ³⁄₃; total 28,—the first permanent premolar having no predecessor in this series. The third incisor, in both upper and lower jaws, is large, developed before the others, and has much the size, form, and direction of the canine. Vertebræ: C 7, D 13-14, L 6, S 4, C 20-24. The hairy covering of the body varies much under different conditions of climate, but when best developed, as in the European Wild Boar, consists of long stiff bristles, mostly abundant on the back and sides, and of a close softer curling undercoat.

The skull of the Pigs (Figs. 103-105) has the axis of the face bent down upon the basicranial axis, as is also the case with the Sheep. Its most striking feature is the elevation and backward slope of the occipital crest formed by the union of the supraoccipital and parietals. The broad and flat frontals have small postorbital processes, which do not join the zygomata, so that the orbits are open behind. The nasals are very long and narrow; and the premaxillæ send up long nasal processes, stopping short of the frontals. A peculiar prenasal bone is developed at the anterior extremity of the mesethmoid, which serves to strengthen the cartilaginous snout. The palate is long and narrow, and extends behind the last molar tooth. In most species the occipital crest is more nearly vertical than in the skull represented in Fig. 104.

[Illustration: FIG. 103.—Left lateral view of the dentition of the Boar (_Sus scrofa_), the roots of the teeth being exposed by removing the external lamina of bone.]

[Illustration: FIG. 104.—Left lateral view of the skull of _Sus longirostris_. ⅕ natural size. (From Nehring.)]

[Illustration: FIG. 105.—Frontal aspect of the cranium of _Sus longirostris_, ⅕ natural size. (From Nehring.)]

This genus occurs at present under three principal modifications or subgenera.

_A._—_Sus_ proper comprises a number of animals found in a wild state throughout the greater part of Europe (except where exterminated by human agency), the north of Africa, southern continental Asia, and the great islands of the Malayan archipelago, Formosa, and Japan. The following among others have been admitted by many zoologists as distinct species:—_Sus scrofa_, the Wild Boar of Europe, Asia Minor, and North Africa, once common throughout the British Isles; _S. sennaarensis_, North-East Africa; _S. cristatus_, India; _S. vittatus_, Java, Borneo, Amboyna, Batchian; _S. papuensis_, New Guinea; _S. timorensis_, Timor and Rotti; _S. andamanensis_, Andaman Islands; _S. taëvanus_, Formosa; _S. leucomystax_, Japan; _S. verrucosus_, Java, Borneo, Ceram; _S. barbatus_, Borneo; _S. celebensis_, Celebes, Philippines, and Moluccas; _S. longirostris_, Borneo and Java. The last four species form an allied group in which the facial portion of the skull may be greatly elongated; _S. barbatus_, and _S. celebensis_ being characterised by the small size and simple structure of the talon of the third molars. The skull of _S. longirostris_ is shown in Figs. 104 and 105. The small _S. andamanensis_ also has very simple third molars. _S. vittatus_, _S. leucomystax_, _S. cristatus_, _S. taëvanus_, and _S. papuensis_ form another group, in which the third molar is generally of very complex structure, more or less closely allied to the Wild Boar; and Dr. Nehring is inclined to think that the whole five might be included under a single specific name. This list will give some idea of the geographical distribution of wild Pigs, but it must be borne in mind that through the whole of this region, and in fact now throughout the greater part of the habitable world, Pigs are kept by man in a domesticated state, and it is still an open question whether some of the wild Pigs of the islands named above may not be local races derived originally from, or crossed with, imported domestic specimens. In New Zealand a wild or rather “feral” race is already established, the origin of which is of course quite recent, since it is well ascertained that no animal of the kind ever lived upon the island until after its settlement by Europeans. Whether the various breeds of domestic Pigs have been derived from one or several sources is still unknown. As in so many similar cases, there is no historic evidence upon the subject, and the researches of naturalists, as Nathusius, Rütimeyer, Rolleston, Nehring, and others, who have endeavoured to settle the question on anatomical evidence, have not led to any satisfactory conclusions. It is, however, tolerably certain that all the species or forms of wild Pigs enumerated above and all the domestic races are closely allied, and it is probable (though of this there has been no opportunity of proof) will breed freely together. It is a curious circumstance that the young of all the wild kinds of Pigs (so far as yet is known) present a uniform coloration, being dark brown with longitudinal stripes of a paler colour, a character which completely disappears after the first few months. On the other hand, this peculiar marking is rarely seen in domestic Pigs in any part of the world, although it has been occasionally observed. It is stated by Darwin that the Pigs which have run wild in Jamaica and the semiferal Pigs of New Granada have resumed this aboriginal character, and produce longitudinally striped young; these must of course be the descendants of domestic animals introduced from Europe since the Spanish conquest, as before that time there were no true Pigs in the New World. Another character by which the European domestic Pig differs from any of the wild species is the concave outline of the frontal region of the skull, a form still retained by the feral Pigs in New Zealand.

_B._—The diminutive Pig of the Nipal, Terai, and Bhutan, _Sus salvanius_, has been separated from the rest by Hodgson under the generic name of _Porcula_, but all the alleged distinctive characters prove on more careful investigation to have little real value. Owing to its retired habits and power of concealment under bushes and long grass in the depths of the great Sal Forest, which is its principal home, very little has been known of this curious little animal, scarcely larger than a hare. The acquisition of living specimens in the London Zoological Gardens has, however, afforded opportunities for careful anatomical observation.[180]

[Illustration: FIG. 106.—Wild Boar and Young.]

_C._—Two well-marked species of African Swine have been with more reason separated under the name of _Potamochœrus_. The dentition differs from that of the true _Sus_, inasmuch as the anterior premolars have a tendency to disappear; sometimes in adult specimens the first upper premolar is retained, but it is usually absent, as well as the first and often the second lower premolars. The molar teeth are also less complex: the last especially having a much less developed talon. There are likewise characteristic cranial differences. The two species are very distinct in outward appearance and coloration. One is _S. africanus_, the South African River-Hog, or Bosch-Vark, of a gray colour, and the other _S. porcus_, the West African Red River-Hog (Fig. 107), remarkable for its vivid colouring and long pencilled ears. It should be noted that the young of both these species, as well as of the pigmy _S. salvanius_, present the striped character of the true _Sus_, a strong indication of close affinities, whereas in all the following forms this is absent.

[Illustration: FIG. 107.—The Red River-Hog (_Sus porcus_). From Sclater, _Guide to Animals in Zoological Society’s Gardens_, 1883, p. 183.]

The genus _Sus_, in the above extended sense, is well represented in the Tertiaries of the Old World from the period of the Lower Pliocene upwards. In the Pliocene and Pleistocene of India _S. falconeri_ and _S. karnuliensis_ are characterised by the extremely complex structure of the molars, in which they show decided signs of approximation to the Wart-Hogs; the same feature being exhibited by _S. phacochœroides_ of the Algerian Pliocene. _S. titan_ and _S. giganteus_, of the Indian Pliocene, together with _S. antiquus_ and _S. erymanthius_, of the corresponding European deposits, are very large species characterised by their comparatively simple molars; _S. titan_ being fully as large as a Tapir. _S. hysudricus_ of the Pliocene of India, and _S. palæochœrus_ of that of Europe, are smaller allied species not improbably related to _S. andamanensis_, with which they agree in molar structure. _S. arvernensis_, of the Upper Pliocene of France, appears to be allied to _S. africanus_; while in the diminutive _S. punjabiensis_ of the Pliocene of North-Western India we probably have the direct ancestor of _S. salvanius_.

[Illustration: FIG. 108.—Head of Babirusa (_Babirusa alfurus_).]

_Babirusa._[181]—Dentition: _i_ ²⁄₃, _c_ ¹⁄₁, _p_ ²⁄₂, _m_ ³⁄₃; total 34. The total number of teeth is therefore considerably reduced, the outer upper incisor and the two anterior premolars of both jaws being absent. The molars, especially the last, are smaller and simpler than in _Sus_; but the great peculiarity of this genus is the extraordinary development of the canines of the male. These teeth (Fig. 108) are ever-growing, long, slender, and curved, and entirely without enamel covering. Those of the upper jaw are directed upwards from their base, so that they never enter the mouth, but piercing the skin of the face, resemble horns rather than teeth, and curve backwards, downwards, and finally often forwards again, almost or quite touching the skin of the forehead. Vertebra: C 7, D 13, L 16, S 4. There is but one species (_B. alfurus_), found only in the islands of Celebes and Buru. Its external surface is almost entirely devoid of hair. With regard to the curiously modified dentition, Wallace (_Malay Archipelago_, vol. i. p. 435) makes the following observations:—“It is difficult to understand what can be the use of these horn-like teeth. Some of the old writers supposed that they served as hooks by which the creature could rest its head on a branch. But the way in which they usually diverge just over and in front of the eye has suggested the more probable idea, that they serve to guard these organs from thorns and spines while hunting for fallen fruits among the tangled thickets of rattans and other spiny plants. Even this, however, is not satisfactory, for the female, who must seek her food in the same way, does not possess them. I should be inclined to believe rather that these tusks were once useful, and were then worn down as fast as they grew, but that changed conditions of life have rendered them unnecessary, and they now develop into a monstrous form, just as the incisors of the Beaver and Rabbit will go on growing if the opposite teeth do not wear them away. In old animals they reach an enormous size, and are generally broken off as if by fighting.”

_Phacochœrus._[182]—The Wart-Hogs, so called from the large cutaneous lobes projecting from each side of the face, have the teeth still more remarkably modified than in _Babirusa_. The milk-dentition, and even the early condition of the permanent dentition, is formed on the same general type as that of _Sus_, except that certain of the typical teeth are absent, the formula being _i_ ¹⁄₃, _c_ ¹⁄₁, _p_ ³⁄₂, _m_ ³⁄₃, total 34; but as age advances all the teeth have a tendency to disappear, except the canines and the posterior molars, which in some cases are the only teeth left in the jaws, and attain an extraordinary development. The upper canines especially are of great size, and curve outwards, forwards, and upwards. Their enamel covering is confined to the apex, and soon wears away. The lower canines are much more slender, but follow the same curve: except on the posterior surface, their crowns are covered with enamel. Unlike those of the Babirusa, the canines of the Wart-Hog are large in both sexes. The third molar tooth of both jaws is of great size, and presents a structure at first sight unlike that of any other mammal, being composed of numerous (22-25) parallel cylinders or columns, each with pulp-cavity, dentine, and enamel covering, and packed together with cement. Careful examination will, however, show that a similar modification to that which has transformed the comparatively simple molar tooth of the Mastodon into the extremely complex grinder of the Indian Elephant has served to change the tooth of the common Pig into that of _Phacochœrus_, and, as already mentioned, some of the fossil Indian and African species of _Sus_ indicate the mode in which this transition came about. The tubercles which cluster over the surface of the crown of the molars of the common Pig are elongated and drawn out into columns in the Wart-Hog, as the low transverse ridges of the Mastodon’s tooth become the leaf-like plates of the Elephant’s.

Two species of this genus are commonly but rather doubtfully distinguished:—_P. africanus_, Ælian’s Wart-Hog, widely distributed over the continent; and _P. æthiopicus_, Pallas’s Wart-Hog, confined to South-Eastern Africa. In specimens attributed to the latter species the dentition reaches its most complete reduction, as in adult animals the upper incisors are absent and the lower ones worn down to the roots.

_Family_ DICOTYLIDÆ.

Snout as in _Suidæ_. Dentition: _i_ ²⁄₃, _c_ ¹⁄₁, _p_ ³⁄₃, _m_ ³⁄₃; total 38. Incisors rooted; upper canines directed downwards, with sharp cutting hinder edges. Toes, four on the fore feet and three on the hind feet (the fifth wanting). Stomach complex. A cæcum. Confined to the New World.

_Dicotyles._[183]—The teeth of the Peccaries (_Dicotyles_) differ from those of the true Pigs (_Sus_) numerically in wanting the upper outer incisor and the anterior premolar on either side of each jaw, and also in the circumstance that the last premolar is nearly as complex as the molars. The upper canines have their points directed downwards, not outwards or upwards as in the Boars, and are very sharp, with cutting hinder edges, and completely covered with enamel until worn. The lower canines are large, directed upwards and outwards, and slightly curved backwards. The premolar and molar teeth form a continuous series, gradually increasing in size from the first to the last. The true molars have square quadricuspidate crowns. The stomach is much more complex than in the true Pigs, almost approaching that of the ruminants. In the feet the two middle (third and fourth) metapodial bones, which are completely separate in the Pigs, are united at their upper ends, as in the ruminants. On the fore foot the two (second and fifth) outer toes are equally developed as in Pigs, but on the hind foot, although the inner (or second) is present, the outer (or fifth) toe is entirely wanting, giving an unsymmetrical appearance of the member, very unusual in Artiodactyles. Vertebræ: C 7, D 14, L 5, S 4, C 7. As in the Pigs, the snout is truncated, and the nostrils are situated in its flat, expanded, disc-like termination. The ears are rather small, ovate, and erect; and there is no external appearance of a tail. The surface of the body is well covered with thick bristly hair, and rather behind the middle of the back is a large and peculiar gland, which secretes an oleaginous substance with a powerful musky odour. This was mistaken by the old travellers for a second navel, a popular error which suggested to Cuvier the name of _Dicotyles_. When the animal is killed for food, it is necessary speedily to remove this gland, otherwise it will taint the whole flesh so as to render it uneatable.

[Illustration: FIG. 109.—The Collared Peccary (_Dicotyles tajacu_).]

There are two species,[184] so nearly allied that they will breed together freely in captivity. Unlike the true Pigs, they never appear to produce more than two young ones at a birth. The Collared Peccary (_D. tajacu_, Linn., _torquatus_, Cuvier), Fig. 109, ranges from the Red River of Arkansas through the forest districts of Central and South America as far as the Rio Negro of Patagonia. Generally it is found singly or in pairs, or at most in small herds of from eight to ten, and is a comparatively harmless creature, not being inclined to attack other animals or human beings. Its colour is dark gray, with a white or whitish band passing across the chest from shoulder to shoulder. The length of the head and body is about 36 inches. The White-lipped Peccary or Warree (_D. labiatus_, Cuvier) is rather larger, being about 40 inches in length, of a blackish colour, with the lips and lower jaw white. Its range is less extensive, since it is not found farther north than British Honduras or south of Paraguay. It is generally met with in large herds of from fifty to a hundred or more individuals, and is of a more pugnacious disposition than the former species, and capable of inflicting severe wounds with its sharp tusks. A hunter who encounters a herd of them in a forest has often to climb a tree as his only chance of safety. Both species are omnivorous, living on roots, fallen fruits, worms, and carrion; and when they approach the neighbourhood of villages and cultivated lands they often inflict great devastation upon the crops of the inhabitants.

Remains of the two existing species of Peccary, as well as of one much larger extinct form, are found in the cavern-deposits of Brazil; while large Peccaries also occur in the Pleistocene of the United States, which, although they have been referred to a distinct genus, _Platygonus_, on account of their relatively smaller incisors and somewhat simpler premolars, may well be included in _Dicotyles_.

[Illustration: FIG. 110.—The three left upper molars of _Hyotherium perimense_, from the Pliocene of India.]

_Allied Extinct Genera._—In the Tertiary deposits of both the Old and New World occur remains of Pig-like animals which, so far as we can judge, appear to connect the Peccaries so closely with the true Pigs as to render the _Dicotylidæ_ really inseparable from the _Suidæ_. Of these the American genus _Chænohyus_ has the lower canine with a triangular cross section and received into a notch in the upper jaw, as in the Peccaries, but the fourth upper premolar is simpler than the molars, as in the under-mentioned genus _Hyotherium_. The typical forms have only three premolars, but in others, which it has been proposed to separate generically as _Bothriolabis_, there are four of these teeth. _Hyotherium_, of the Pliocene and Miocene of the Old World, is a generalised form allied both to _Sus_ and _Dicotyles_ as well as to certain extinct genera. The upper molars (Fig. 110) are characterised by their square crowns, the last having no distinct third lobe, and coming into use before the first is much worn, while the last premolar is simpler than the true molars. The canines, which have an oval section and are scarcely larger than the incisors, are not received into a notch in the upper jaw. In the Pliocene of India there occurs an apparently allied genus known as _Hippohyus_, in which the crowns of the molars are much taller, and have lateral infoldings of the enamel, producing a very complex pattern on the worn crowns. The European Miocene genus _Listriodon_, with the dental formula _i_ ³⁄₃, _c_ ¹⁄₁, _p_ ³⁄₃, _m_ ³⁄₃, differs from all the preceding in having the anterior and posterior pairs of tubercles of the molars united into ridges running across their crowns, so that these teeth resemble the lower molars of the Tapir. The genus is also found in the Lower Pliocene of India.

EXTINCT TRANSITIONAL ARTIODACTYLES.

In this place it will be convenient to notice briefly a few of the extinct types of Tertiary Artiodactyles which connect the existing bunodont Suina with the more specialised selenodont groups mentioned below so closely as to show that in a strictly palæontological classification such groups cannot be maintained. It should be mentioned that while some of these extinct forms were in all probability actual ancestral links between the bunodonts and selenodonts, others, like the Anoplotheres, died out entirely without giving rise to any more specialised descendants.

[Illustration: FIG. 111.—The imperfect third left upper molar of _Hyopotamus giganteus_, Miocene, India. (From the _Palæontologia Indica_.)]

_Chœropotamidæ._—In this family the molars are intermediate in structure between those of the _Suidæ_ and the next family. The upper ones have very broad crowns, with the five columns arranged as in _Anthracotherium_; while the premolars are not secant, and may be very large. The best known forms are the small _Cebochœrus_ of the Phosphorites of Central France; _Chœropotamus_ of the Upper Eocene, the type species of which was of the size of a large Pig, with the dental formula _i_ ³⁄₃, _c_ ¹⁄₁, _p_ ⁴⁄₃, _m_ ³⁄₃, and no distinctly selenodont structure in the molars; the much larger _Elotherium_, from the Upper Eocene and Lower Miocene of both the Old and New Worlds, which presents the very rare feature of the absence of a third lobe to the last lower molar; and the equally large _Tetraconodon_ of the Pliocene of India, in which this third lobe was present and the premolars were of enormous size. The remarkable North American Eocene genus _Achænodon_ should perhaps also be placed here.

[Illustration: FIG. 112.—A right upper molar of _Merycopotamus pusillus_, Pliocene, India. (From the _Palæontologia Indica_.)]

_Anthracotheriidæ._—The genera _Anthracotherium_ and _Hyopotamus_, of the upper Eocene and Miocene, have the typical Eutherian dental formula; the upper molars (Fig. 111) carrying three columns on the anterior and two on the posterior half of the crown, all of which are of a more or less decidedly selenodont structure. The mandible has a descending flange at the angle. The figured tooth (in which the antero-internal and antero-median columns are imperfect) may be compared with the diagram given in Fig. 5, p. 32, when the homology of the columns or tubercles will be at once apparent, the broken antero-median column representing the protoconule. Some of the species are of large size, while others are comparatively small.

_Merycopotamus._—The genus _Merycopotamus_ of the lower Pliocene of India may be regarded as an Anthracotheroid which has lost the antero-median column to the upper molars (Fig. 112), so that these teeth are consequently quadrituberculate; and may thus be regarded as typical examples of the brachy-selenodont modification of molar structure.

_Cotylopidæ._—The Miocene genus _Cotylops_ (_Oreodon_[185]) is the type of a large American family in which the upper molars are selenodont and usually have four columns, while the lower canine is approximated to the incisors and its form and function assumed by the first premolar. The last upper premolar is simpler than the molars. There is no flange to the angle of the mandible; and the feet have four digits. The affinities of this peculiar family are probably widely spread, but they may have been derived from the _Anthracotheriidæ_. The type genus has the full Eutherian dentition, but in some of the more specialised forms (_Cyclopidius_) the upper incisors may be wanting, and large vacuities occur in the lachrymal region. The generalised genus _Protoreodon_, of the Upper or Uinta Eocene, has five cusps on the upper molars, arranged as in the _Anthracotheriidæ_. The pollex is retained in the manus of the type genus.

[Illustration: FIG. 113.—Restoration of _Anoplotherium commune_ (Upper Eocene). Cuvier.]

The family may be divided into subfamilies as follows:—

I. Upper molars with four columns.

1. Orbits open, no lachrymal fossa, a diastema, the last upper premolar with two outer columns, outer wall of upper molars concave and inclined inwards.—_Agriochœrinæ_ (_Agriochœrus_).

2. Orbits closed, a lachrymal fossa, no diastema, the last upper premolar with one outer column; outer wall of upper molars flattened.—_Cotylopinæ_ (_Cotylops_, _Eporeodon_, _Merycochœrus_, _Cyclopidius_, etc.)

II. Upper molars with five columns.—_Protoreontinæ_ (_Protoreodon_).

_Anoplotheriidæ._—This family includes several Upper Eocene European genera, with selenodont upper molars, carrying five columns arranged as those in _Anthracotherium_. One of the earliest known, _Anoplotherium_, was fully described by Cuvier from remains found in the Paris gypsum-beds (Upper Eocene). Its forty-four teeth formed a series unbroken by a gap or diastema, and were of uniform height (as in Man alone of existing mammals). Its tail was long, with large chevron bones underneath, not usually found in Ungulates, and there were either three or two toes on each foot. It was in many respects a much-specialised form, apparently not on the line of descent of any of the existing groups.

_Dacrytherium_ is an allied genus whose dentition leads on to that of the smaller _Xiphodon_. The latter genus is characterised by the compressed and elongated form of the crowns of the first three premolars, which thus approximate to those of the Chevrotains. There were only two functional digits to the feet. The so-called _Hyopotamus picteti_, of the Swiss Eocene, is a species of _Dacrytherium_.

_Cænotheriidæ._—The typical representatives of this family are small animals not larger than the Chevrotains, with the full complement of teeth, generally no marked gap in the series, and the crowns of the upper molars carrying two columns on the anterior and three on the posterior half of the crown—precisely the reverse of the arrangement obtaining in the _Anthracotheriidæ_. The known forms are from the Upper Eocene and Lower Miocene of Europe. In _Cænotherium_ the molars are selenodont, while they are bunodont in _Dichobunus_. _Homacodon_, of the Bridger Eocene of the United States, is closely allied to the latter. The first lower premolar of _Dichobunus_ assumes the form and function of a canine. _Spaniotherium_ (_Metriotherium_) is a much larger form, in which the molars are not unlike those of _Anthracotherium_, if the arrangement of the cusps were reversed; it occurs in the Eocene Phosphorites of France. It is suggested that the _Tylopoda_ may have originated from this group.

_Tapirulus_ is a small Eocene Artiodactyle with the columns of the upper molars, which are somewhat like those of _Hyopotamus_, tending to form transverse ridges; its family position is uncertain.

_Dichodontidæ._—The European genera included in this family all have quadritubercular selenodont molars, and show signs of approximating more or less closely to existing types. _Dichodon_, from the Upper Eocene and Lower Miocene, has the full complement of teeth, which show no diastema, and have low crowns. The fourth upper premolar has four columns, like the true molars, and the corresponding lower tooth three complete lobes; these features being unknown in any other Selenodonts. In _Lophiomeryx_, of the same beds, the somewhat higher crowns of the molars approximate to those of the _Cervidæ_, but the hinder lobes of the upper ones are imperfectly developed; the genus may be allied, to the _Tragulidæ_. In the small _Gelocus_, of the Lower Miocene, the molars are not unlike those of _Dichodon_; but the navicular and cuboid bones of the tarsus were fused together, and the metatarsals had united to form a “cannon-bone,” although the metacarpals still remained distinct. It is not improbable that upper incisors were wanting; and it has been suggested that we have in this genus the ancestral type of the _Tragulidæ_ and _Cervidæ_.

TYLOPODA.

_Family_ CAMELIDÆ.

This group is represented at the present day by the two species of Camels of the Old World and the Llamas of South America, collectively constituting the family _Camelidæ_. The special characters which the Llamas and Camels have in common, and the combination of which distinguishes them from the rest of the Artiodactyles, are as follows. The premaxillæ have the full number of incisor teeth in the young state, and the outermost is persistent through life as an isolated laniariform tooth. The canines are present in both jaws, and those of the mandible are differentiated from the long, procumbent, and spatulate incisors, being suberect and pointed. The crowns of the true molars belong to the crescentic or selenodont type, and are very hypsodont; but one or more of the anterior premolars is usually detached from the series, and is of simple pointed form. The auditory bulla is filled with cancellous tissue. The hinder part of the body is much contracted, and the femur long and vertically placed, so that the knee-joint is lower in position, and the thigh altogether more detached from the abdomen than in most quadrupedal mammals. The limbs are long, but with only the third and fourth digits developed; no traces of any of the others being present. The trapezoid and magnum of the carpus, and the cuboid and navicular of the tarsus are distinct. The two metapodial bones of each limb are confluent for the greater part of their length, though separated for a considerable distance at the lower end. Their distal articular surfaces, instead of being pulley-like, with deep ridges and grooves, as in other recent Artiodactyles, are simple, rounded, and smooth. The proximal phalanges are expanded at their distal ends, and the wide, depressed middle phalanges are embedded in a broad cutaneous pad, forming the sole of the foot, on which the animal rests in walking, instead of on the hoofs. The ungual phalanges are very small and nodular, not flattened on their inner or opposed surfaces, and not completely encased in hoofs, but bearing nails on their upper surface only. The cervical region is long and flexuous, and the vertebræ of which it is composed are remarkable for the position of the canal for the transmission of the vertebral artery, which does not perforate the transverse process, but passes obliquely through the anterior part of the pedicle of the arch (a condition only found in two other genera of mammals, _Macrauchenia_ and _Myrmecophaga_). There are no horns or antlers. Though these animals ruminate, the stomach differs considerably in the details of its construction from that of the Pecora. The interior of the rumen or paunch has no villi on its surface, and there is no distinct psalterium or manyplies. Both the first and second compartments are remarkable for the presence of a number of pouches or cells in their walls, with muscular septa, and a sphincter-like arrangement of their orifices, by which they can be shut off from the rest of the cavity, and into which the fluid portion only of the contents of the stomach is allowed to enter.[186] The placenta is diffuse, as in the Suina and Tragulina, not cotyledonary, as in the Pecora. Finally, the _Camelidæ_ differ not only from other Ungulates, but from all other mammals, in the fact that the red corpuscles of the blood, instead of being circular in outline, are oval, as in the inferior vertebrated classes.

_Camelus._[187]—Dentition of adult: _i_ ¹⁄₃, _c_ ¹⁄₁, _p_ ³⁄₂, _m_ ³⁄₃; total 34. First upper premolar simple, placed immediately behind the premaxillæ, and separated by a long diastema from the penultimate tooth of that series. Lower incisors somewhat proclivous, the outermost the largest. Skull elongated, with an overhanging occiput, orbits completely surrounded by bone, and the premaxillæ not articulating with the arched and somewhat elongated nasals. Vertebræ: C 7, D 12, L 7, S 4, C 13-15. Ears comparatively short and rounded. One or two dorsal adipose humps. Feet broad, with the toes very imperfectly separated. Tail well developed, tufted at the end. Hair nearly straight, and not woolly. Size very large and bulky.

The genus is now represented by two species, viz. the single-humped Arabian Camel (_Camelus dromedarius_), and the double-humped Bactrian Camel (_C. bactrianus_, Fig. 114).[188] The former is quite unknown in a wild state, but it is reported that wild Bactrian Camels occur in the more remote parts of Turkestan. The latter species is found in a domesticated state throughout a large portion of Turkestan and the neighbouring region, extending as far as the Crimea in the west and to Lake Baikal and Pekin in the east. It is a heavier and more clumsy animal than the Arabian Camel, with thicker hair, shorter legs, and the feet more callous and better adapted to a hard ground. The hair is most developed upon the top of the head, neck, humps, arm, and wrist. Bactrian Camels are occasionally brought over the stupendous mountain passes south of Yarkand to within a few days’ journey of Leh, in Kashmir territory.

[Illustration: FIG. 114.—The Bactrian Camel (_Camelus bactrianus_).]

The Arabian Camel is commonly employed as a beast of burden in Africa and India, and has of late years been introduced into Australia for the same purpose; it is especially valuable in crossing long stretches of arid desert from its power of existing for a considerable period of time without water. The female goes fully eleven months with young, and produces but a single calf at a birth, which is suckled for a whole year. In disposition the Camel is surly and subject to furious outbursts of temper, especially during the rutting season. At such periods the male utters a peculiar and highly disagreeable bubbling noise in its throat, well known to all who have travelled in India with Camels as their transport. It has been said that the Camel is docile, but Palgrave observes:—

“If docile means stupid, well and good; in such a case the Camel is the very model of docility. But if the epithet is intended to designate an animal that takes an interest in its rider so far as a beast can, that in some way understands his intentions, or shares them in a subordinate fashion, that obeys from a sort of submissive or half-fellow-feeling with his master, like the horse or elephant, then I say that the camel is by no means docile—very much the contrary. He takes no heed of his rider, pays no attention whether he be on his back or not, walks straight on when once set agoing, merely because he is too stupid to turn aside, and then should some tempting thorn or green branch allure him out of the path, continues to walk on in the new direction simply because he is too dull to turn back into the right road. In a word, he is from first to last an undomesticated and savage animal, rendered serviceable by stupidity alone, without much skill on his master’s part, or any co-operation on his own save that of an extreme passiveness. Neither attachment nor even habit impress him; never tame, though not wide-awake enough to be exactly wild.” The two species breed together freely, and among the Yourouks of Asia Minor, hybrids, or mules, the produce generally of a male Bactrian and a female Arabian camel are preferred to either of the pure breeds.

Fossil remains of Camels are found in the Pliocene of the Siwalik Hills in Northern India. These differ from the existing representatives of the genus in having a vertical ridge at the antero-external angle of the lower molars, whereby they resemble _Auchenia_; their cervical vertebræ are also intermediate in structure between those of the latter and the existing Camels. A fossil Camel is also found in the Pleistocene of Algeria.

_Auchenia._[189]—Dentition of adults normally: _i_ ¹⁄₃, _c_ ¹⁄₁, _p_ ²⁄₂, _m_ ³⁄₃; total 32—one of the lower premolars may, however, be wanting. In the upper jaw there is a compressed, sharp, pointed laniariform incisor near the hinder edge of the premaxilla, followed, in the male at least, by a moderate-sized, pointed, curved true canine in the anterior part of the maxilla. The isolated canine-like premolar which follows in the Camels is not present. The teeth of the molar series, which are in contact with each other, consist of two very small premolars (the first almost rudimentary) and three broad molars, constructed generally like those of _Camelus_. In the lower jaw the three incisors are long, spatulate, and procumbent; the outer ones being the smallest. Next to these is a curved, suberect canine, followed after an interval by an isolated, minute, and often deciduous simple conical premolar; then a contiguous series of one premolar and three molars, which differ from those of existing species of _Camelus_ in having a small accessory column at the anterior outer edge. The skull generally resembles that of _Camelus_, the relatively larger brain-cavity and orbits and less developed cranial ridges being due to its smaller size. The nasal bones are shorter and broader, and are joined by the premaxillæ. Vertebræ: C 7, D 12, L 7, S 4, C 15-20. Ears rather long and pointed. No dorsal hump. Feet narrow, the toes being more separated than in the camels, each having a distinct plantar pad. Tail short. Hairy covering long and woolly. Size (in existing forms) smaller, and general form lighter than in the Camels. At present and within historic times the genus is entirely confined to the western side and southernmost parts of South America, but fossil remains have been found in the caves of Brazil, in the pampas of the Argentine republic, and in Central and North America.

[Illustration: FIG. 115.—Llama (_Auchenia glama_), from an animal living in the Gardens of the Zoological Society of London.]

The word Llama, sometimes spelt Lama, is the name by which the Peruvians designated one of a small group of closely allied animals, which, before the Spanish conquest of America, were the only domesticated hoofed mammals of the country, being kept, not only for their value as beasts of burden, but also for their flesh, hides, and wool,—in fact, supplying in the domestic economy of the people the place of the horse, the ox, the goat, and the sheep of the Old World. The word is now sometimes restricted to one particular species or variety of the group, and sometimes used in a generic sense to cover the whole. Although they were often compared by early writers to sheep, and spoken of as such, their affinity to the camel was very soon perceived, and they were included in the genus _Camelus_ in the _Systema Naturæ_ of Linnæus. They were, however, separated by Cuvier in 1800 under the name of _Lama_, changed by Illiger in 1811 to _Auchenia_ (in allusion to the great length of neck, αὐχήν), a term afterwards adopted by Cuvier, and almost universally accepted by systematic zoologists, although there has been of late a disposition to revive the earlier name.

In essential structural characters, as well as in general appearance and habits, all the animals of this genus very closely resemble each other, so that the question as to whether they should be considered as belonging to one, two, or more species has been one which has led to a large amount of controversy among naturalists. The question has been much complicated by the circumstances of the great majority of individuals which have come under observation being either in a completely or partially domesticated state, and descended from ancestors which from time immemorial have been in like condition, one which always tends to produce a certain amount of variation from the original type. It has, however, lost much of its importance since the doctrine of the distinct origin of species has been generally abandoned.

[Illustration: FIG. 116.—Head of Vicugna, from an animal living in the Gardens of the Zoological Society of London.]

The four forms commonly distinguished by the inhabitants of South America are recognised by some naturalists as distinct species, and have had specific designations attached to them, though usually with expressions of doubt, and with great difficulties in defining their distinctive characteristics. These are (1) the Llama, _Auchenia glama_ (Linn.), or _Lama peruana_ (Tiedemann); (2) the Alpaca, _A. pacos_ (Linn.); (3) the Guanaco or Huanaco, _A. huanacus_ (Molina); and (4) the Vicugna, _A. vicugna_ (Molina), or _A. vicunna_, (Cuv.) The first and second are only known in the domestic state, and are variable in size and colour, being often white, black, or piebald. The third and fourth are wild, and of a nearly uniform light-brown colour, passing into white below. They certainly differ from each other, the Vicugna being smaller, more slender in its proportions, and having a shorter head (Fig. 116) than the Guanaco (Fig. 117). It may therefore, according to the usual view of species, be considered distinct. It lives in herds on the bleak and elevated parts of the mountain range bordering the region of perpetual snow, amidst rocks and precipices, occurring in various suitable localities throughout Peru, in the southern part of Ecuador, and as far south as the middle of Bolivia. Its manners very much resemble those of the Chamois of the European Alps; and it is as vigilant, wild, and timid. The wool is extremely delicate and soft, and highly valued for the purposes of weaving, but the quantity which each animal produces is not great.

[Illustration: FIG. 117.—Head of Guanaco, from an animal living in the Gardens of the Zoological Society of London.]

The Guanaco has an extensive geographical range, from the highlands of the Andean region of Ecuador and Peru to the open plains of Patagonia, and even the wooded islands of Tierra del Fuego. It constitutes the principal food of the Patagonian Indians, and its skin is invaluable to them, as furnishing the material out of which their long robes are constructed. It is about the size of a European Red Deer, and is an elegant animal, being possessed of a long, slender, gracefully curved neck and fine legs. Dr. Cunningham,[190] speaking from observation on wild animals, says:—

“It is not easy to describe its general appearance, which combines some of the characters of a camel, a deer, and a goat. The body, deep at the breast but very small at the loins, is covered with long, soft, very fine hair, which on the upper parts is of a kind of fawn-colour, and beneath varies from a very pale yellow to the most beautiful snow-white. The head is provided with large ears, in general carried well back, and is covered with short grayish hair, which is darkest on the forehead. Occasionally the face is nearly black. As a rule it lives in flocks of from half a dozen to several hundreds, but solitary individuals are now and then to be met with. They are very difficult to approach sufficiently near to admit of an easy shot, as they are extremely wary, but, on being disturbed, canter off at a pace which soon puts a safe distance between them and the sportsman, even though he should be mounted. Despite their timidity, however, they are possessed of great curiosity, and will sometimes advance within a comparatively short distance of an unknown object, at which they will gaze fixedly till they take alarm, when they effect a speedy retreat. Their cry is very peculiar, being something between the belling of a deer and the neigh of a horse. It would be difficult to overestimate their numbers upon the Patagonian plains; for in whatever direction we walked we always came upon numbers of portions of their skeletons and detached bones.”

Darwin, who has given an interesting account of the habits of the Guanaco in his _Naturalist’s Voyage_, says that they readily take to the water, and were seen several times at Port Valdes swimming from island to island.

The Llama is only known as a domestic animal, and is chiefly met with in the southern part of Peru. Burmeister, a very competent writer on the subject, says that he is perfectly satisfied that it is the descendant of the wild Guanaco, an opinion opposed to that of Tschudi. It generally attains a larger size than the Guanaco, and is usually white or spotted with brown or black, and sometimes altogether black. The earliest and often-quoted account of this animal by Agustin de Zarate, treasurer-general of Peru in 1544, will bear repeating as an excellent summary of the general character and uses to which it was put by the Peruvians at the time of the Spanish conquest. He speaks of the Llama as a sheep, observing, however, that it is camel-like in shape though destitute of a hump:—

“In places where there is no snow the natives want water, and to supply this they fill the skins of sheep with water and make other living sheep carry them; for, it must be remarked, these sheep of Peru are large enough to serve as beasts of burden. They can carry about one hundred pounds or more, and the Spaniards used to ride them, and they would go four or five leagues a day. When they are weary they lie down upon the ground; and as there are no means of making them get up, either by beating or assisting them, the load must of necessity be taken off. When there is a man on one of them, if the beast is tired and urged to go on, he turns his head round and discharges his saliva, which has an unpleasant odour, into the rider’s face. These animals are of great use and profit to their masters, for their wool is very good and fine, particularly that of the species called Pacas, which have very long fleeces; and the expense of their food is trifling, as a handful of maize suffices them, and they can go four or five days without water. Their flesh is as good as that of the fat sheep of Castile. There are now public shambles for the sale of their flesh in all parts of Peru, which was not the case when the Spaniards came first; for when one Indian had killed a sheep his neighbours came and took what they wanted, and then another Indian killed a sheep in his turn.”

The disagreeable habit here noticed of spitting in the face of persons whose presence is obnoxious is common to all the group, as may be daily witnessed in specimens in confinement in the menageries of Europe. One of the principal labours to which the Llamas were subjected at the time of the Spanish conquest was that of bringing down ore from the mines in the mountains. Gregory de Bolivar estimated that in his day as many as three hundred thousand were employed in the transport of the produce of the mines of Potosi alone; but since the introduction of horses, mules, and donkeys the importance of the Llama as a beast of burden has greatly diminished.

The Alpaca, though believed by many naturalists to be a variety of the Vicugna, is more probably, like the Llama, derived from the Guanaco, having the naked callosities on the hind limbs, and the relatively large skull of the latter. It is usually found in a domesticated or semi-domesticated state, being kept in large flocks which graze on the level heights of the Andes of southern Peru and northern Bolivia at an elevation of from 14,000 to 16,000 feet above the sea-level, throughout the year. It is smaller than the Llama, and, unlike that animal, is not used as a beast of burden, but is valued only for its wool, of which the Indian blankets and ponchas are made. Its colour is usually dark brown or black.

Mention has already been made of the occurrence of fossil Llamas in America, but some diversity of view obtains as to the generic position of some of these forms, owing to variations in their dental formula. Remains apparently referable to the existing species occur in the cavern-deposits of Brazil. In the Pleistocene of Mexico we meet with _A. (Palauchenia) magna_, which attained the size of a Camel, and had always two, and occasionally three, lower premolars; while in one South American Pleistocene species, which has been generically separated as _Hemiauchenia_, there were invariably three premolars in each jaw. In _A. (Holomeniscus) hesterna_, from the Pleistocene of North America, which was equal in size to _A. magna_, the premolars were reduced to one in each jaw; and the same condition obtains in _A. (Eschatius) vitakeriana_, where, however, the upper one is of simpler structure.

_Extinct Cameloids._—Until within the last few years the existence of two genera having so very much in common as the Camels and the Llamas, and yet so completely isolated geographically, had not received any satisfactory explanation; for the old idea that they in some way “represented” each other in the two hemispheres of the world was a mere fancy without philosophical basis. The discoveries made mostly within the past twenty years of a vast and previously unsuspected extinct fauna in the American continent of the Tertiary period, as interpreted by Leidy, Cope, Marsh, and others, has thrown a flood of light upon the early history of this family, and upon its relations to other mammals.

There have been found in these regions many Camel-like animals exhibiting different generic modifications; and, what is more interesting, a gradual series of changes, coinciding with the antiquity of the deposits in which they are found, have been traced from the thoroughly differentiated species of the modern epoch down through the Pliocene to the early Miocene beds, where, their characters having become by degrees more generalised, they have lost all that specially distinguishes them as _Camelidæ_, and are merged into forms common to the ancestral type of all the other sections of the Artiodactyles. Hitherto none of these annectant forms have been found in any of the fossiliferous strata of the Old World; and it may therefore be fairly surmised (according to the evidence at present before us) that America was the original home of the Tylopoda, and that the true Camels have passed over into the Old World, probably by way of the north of Asia, where we have every reason to believe there was formerly a free communication between the continents, and then, gradually driven southward, perhaps by changes of climate, having become isolated, have undergone some further special modifications; while those members of the family that remained in their original birthplace have become, through causes not clearly understood, restricted solely to the southern or most distant part of the continent. The occurrence in the dentition of the fossil Siwalik Camels of a feature now found only in _Auchenia_ is especially interesting from this point of view.

Briefly referring to some of these fossil types, we may note that _Pliauchenia_, of the Loup Fork beds (Lower Pliocene) of the United States, has three lower premolars, while in _Procamelus_ there were four of these teeth. In _Protolabis_ of the Miocene we have a more generalised form, in which the dental formula is _i_ ³⁄₃, _c_ ¹⁄₁, _p_ ⁴⁄₄, _m_ ³⁄₃; and from this type a transition may be traced to _Poëbrotherium_, which, while having the same dental formula, was no larger than a Fox, and had the third and fourth metacarpals separate, with rudiments of the fourth and fifth. The earliest undoubted representative of the group is _Leptotragulus_, of the Uinta Eocene, which appears to have been closely allied to _Poëbrotherium_. It is, however, probable that the first lower premolar was wanting; while the other premolars of the mandible were much shorter antero-posteriorly than in the last-named genus. The manus, moreover, appears to have been less reduced, the second metacarpal retaining its connection with the magnum. It is suggested that _Leptotragulus_ may have been derived from the Bunodont genus _Homacodon_ of the Bridger Eocene, mentioned among the _Cænotheriidæ_.

TRAGULINA.

_Family_ TRAGULIDÆ.

No teeth in premaxillæ. Upper canines well developed, especially in the males; narrow and pointed. Lower canines incisiform. No caniniform premolars in either jaw, all the premolars except the last in the upper jaw being secant. Molariform teeth in a continuous series, consisting of _p_ ³⁄₃, _m_ ³⁄₃. Odontoid process of axis vertebra conical. Fibula complete. Four complete toes on each foot. The middle metapodials generally confluent, the outer ones (second and fifth) very slender but complete, _i.e._ extending from the carpus or tarsus to the digit. Navicular, cuboid, and ectocuneiform bones of tarsus united. Tympanic bullæ of skull filled with cancellar tissue. No frontal appendages. Ruminating, but the stomach with only three distinct compartments, the manyplies or third cavity of the stomach of the Pecora being rudimentary. Placenta diffused.

This section is represented only by the single family _Tragulidæ_, containing a few animals of small size, commonly known as Chevrotains, intermediate in their structure between the Deer, the Camels, and the Pigs. The large size of the canines of the male and the absence of horns caused them to be associated formerly with _Moschus_, one of the _Cervidæ_; hence they are often spoken of as “Pigmy Musk-Deer,” although they have no musk-secreting gland, or, except in the above-named trivial external characters, no special affinities with the true Musk-Deer. There has scarcely been a more troublesome and obdurate error in zoology than in this association of animals so really distinct. It has been troublesome, not only in preventing a just conception of the relations of existing Artiodactyles, but also in causing great confusion and hindrance in palæontological researches among allied forms; and most obdurate, inasmuch as all that has been recently done in advancing our knowledge of both groups has not succeeded in eradicating it, not only from nearly every one of our zoological text-books, whether British or Continental, but even from works of the highest scientific pretensions.

The family is now generally divided into two genera.

_Tragulus_,[191] containing the smallest of the existing Ungulates, animals having more of the general aspects and habits of some Rodents, as the Agoutis, than of the rest of their own order. The best-known species are _T. javanicus_, _T. napu_, _T. stanleyanus_, and _T. memmina_. The first three are from the Malay Peninsula, or the islands of the Indo-Malayan Archipelago, the last from Ceylon and India. A fossil species occurs in the Pliocene of the latter country.

_Dorcatherium_[192] is distinguished chiefly by the feet being stouter and shorter, the outer toes better developed, and the two middle metacarpals not ankylosed together. Its dental formula (as that of _Tragulus_) is usually _i_ ⁰⁄₃, _c_ ¹⁄₁, _p_ ³⁄₃, _m_ ³⁄₃ = 34. Vertebræ: C 7, D 13, L 6, S 5, C 12-13. The only existing species, _D. aquaticum_ (Fig. 118), from the west coast of Africa, is rather larger than any of the Asiatic Chevrotains, which it otherwise much resembles, but it is said to frequent the banks of streams, and have much the habits of Pigs. It is of a rich brown colour, with back and sides spotted and striped with white. It is evidently the survivor of a very ancient form, as remains of the type species (_D. naui_), only differing in size, occur in the lower Pliocene and Miocene of Europe; fossil species are also found in the Indian Pliocene. In _D. naui_ there are, at least frequently, four lower premolars, while the existing species has but three of these teeth.

[Illustration: FIG. 118.—The African Water-Chevrotain (_Dorcatherium aquaticum_).]

_Extinct Traguloids._—A number of small selenodont Artiodactyles from various Miocene and Pliocene deposits appear to connect the modern Tragulina so closely with _Gelocus_ (p. 294), and thus with the ancestral _Cervidæ_, that their classification is almost an impossibility. Thus _Leptomeryx_, from the Miocene of the United States, is regarded as a Traguloid, having four premolars in each jaw and with the metatarsals fused into a cannon-bone. _Prodremotherium_, of the Upper Eocene Phosphorites of France, differs in that the metacarpals also form a cannon-bone; while in the American _Hypertragulus_, both metacarpals and metatarsals remain separate. _Bachitherium_, of the French Phosphorites, apparently presents affinity with _Gelocus_, _Prodremotherium_, and _Dorcatherium_. In this genus the first of the four lower premolars assumes the character and function of a canine, the true canine being incisor-like, and there are traces of minute upper incisors.

PECORA, OR COTYLOPHORA.

No premaxillary teeth or caniniform premolars. Upper canines generally absent, though sometimes largely developed. Inferior incisors, three on each side with an incisiform canine in contact with them. Molariform teeth consisting of _p_ ³⁄₃, _m_ ³⁄₃, in continuous series. Auditory bullæ simple and hollow within. Odontoid process in the form of a crescent, hollow above. Distal extremity of the fibula represented by a distinct malleolar bone of peculiar shape, articulating with the outer surface of the lower end of the tibia. Third and fourth metacarpals and metatarsals confluent. Outer or lateral toes small and rudimentary, or in some cases entirely suppressed; their metapodial bones never complete in existing forms. Navicular and cuboid bones of tarsus united. Horns or antlers usually present, at least in the male sex. Left brachial artery arising from a common innominate trunk, instead of coming off separately from the aortic arch as in the preceding sections. Stomach with four complete cavities. Placenta cotyledonous.[193]

[Illustration: FIG. 119.—A shed right antler of the Red Deer (_Cervus elaphus_), found in an Irish lake. _a_, Brow tine; _b_, bez tine; _c_, tres tine; _d_, crown or royal tine. (After Owen.)]

The Pecora or true Ruminants form at the present time an extremely homogeneous group, one of the best-defined and most closely united of any of the Mammalia. But, though the original or common type has never been departed from in essentials, variation has been very active among them within certain limits; and the great difficulty which all zoologists have felt in subdividing them into natural minor groups arises from the fact that the changes in different organs (feet, skull, frontal appendages, teeth, cutaneous glands, etc.) have proceeded with such apparent irregularity and absence of correlation that the different modifications of these parts are most variously combined in different members of the group. It appears, however, extremely probable that they soon branched into two main types, represented in the present day by the _Cervidæ_ and the _Bovidæ_,—otherwise the antlered and horned Ruminants. Intermediate smaller branches produced the existing Musk-Deer and Giraffe, as well as the extinct _Helladotherium_ inclining to the first-named group, and the extinct _Sivatherium_, _Brahmatherium_, _Hydaspitherium_, and others more allied to the latter, although upon the true relationship of these forms there is a difference of opinion.

[Illustration: FIG. 120.—Head of Deer (_Cervus schomburgki_), showing antlers. From Sclater, _Proc. Zool. Soc._ 1877, p. 682.]

The earliest forms of true Pecora, as _Palæomeryx_, generally had no frontal appendages, and some few forms continue to the present day in a similar case. In the very large majority, however, either in both sexes or in the male only, a pair or occasionally two pairs (_Tetraceros_ and the extinct _Sivatherium_) of processes are developed from the frontal bones as weapons of offence and defence, these being almost always formed on one or other of two types.

1. “Antlers” are outgrowths of true bone, covered during their growth with vascular, sensitive integument coated with short hair. When the growth of the antler is complete, the supply of blood to it ceases, the skin dies and peels off, leaving the bone bare and insensible, and after a time, by a process of absorption near the base, it becomes detached from the skull and is “shed” (Fig. 119). A more or less elongated portion or “pedicle” always remains on the skull from the summit of which a new antler is developed. In the greater number of existing species of Deer this process is repeated with great regularity at the same period of each year. The antler may be simple, straight, subcylindrical, tapering and pointed, but more often it sends off one or more branches called “tines” or “snags” (Fig. 119). In this case the main stem is termed the “beam.” Commonly all the branches of the antler are cylindrical and gradually tapering. Sometimes they are more or less expanded and flattened, the antler being then said to be “palmated.” In young animals the antlers are always small and simple, and in those species in which they are variously branched or palmated, this condition is only gradually acquired in several successive annual growths. An interesting parallel has been observed here, as in so many other cases, between the development of the race and that of the individual. Thus the earliest known forms of Deer, those of the Lower Miocene, generally have no antlers, as in the young of the existing species. The Deer of the Middle Miocene have simple antlers, with not more than two branches, as in existing Deer of the second year; but it is not until the Pliocene and Pleistocene times that Deer occur with antlers developed with that luxuriance of growth and beauty of form characteristic of some of the existing species in a perfectly adult state. Among recent _Cervidæ_, antlers are wanting in the genera _Moschus_ and _Hydropotes_; they are present in both sexes in _Tarandus_ (the Reindeer), and in the male sex only in all others.

In those forms with the most complex antlers (Figs. 119, 120) the tine immediately over the forehead is termed the _brow tine_, the next one the _bez tine_, and the third one the _tres tine_; the mass of points at the summit of the antler being termed either the _royal_ and _surroyal tines_, or collectively the _crown_. The nodulated bony ring at the base of the antler, just above the point at which it separates from the pedicle when it is shed, is termed the _burr_.

[Illustration: FIG. 121.—Head of Antelope (_Gazella granti_), showing horns. From Sir V. Brooke, _Proc. Zool. Soc._ 1878, p. 724.]

2. The horns of the _Bovidæ_ consist of permanent, conical, usually curved bony processes, into which air-cells continued from the frontal sinuses often extend, called “horn-cores,” ensheathed in a case of true horn, an epidermic development of fibrous structure, which grows continuously, though slowly, from the base, and wears away at the apex, but is very rarely shed entire. The only existing species in which the latter process occurs regularly and periodically is the American Prong-Buck (_Antilocapra_), in which the horns also differ from those of all others in being bifurcated. Horns are not present at birth, but begin to grow very soon afterwards. The males of all existing _Bovidæ_ possess them, and they are also present (though usually not so fully developed) in the females of all except the genera _Boselaphus_, _Strepsiceros_, _Tragelaphus_, _Antilope_, _Æpyceros_, _Saiga_, _Cobus_, _Cervicapra_, _Pelea_, _Nanotragus_, _Neotragus_, _Cephalophus_, and _Tetraceros_; as well as in some species of _Gazella_, such as _G. picticandata_ and _G. walleri_.

[Illustration: FIG. 122.—Crown surface of a worn left upper molar of _Palæomeryx sivalensis_, to show brachydont type. (From the _Palæontologia Indica_.)]

Another character by which different members of the _Pecora_ can be distinguished among themselves is derived from the nature of the molar teeth. Although there is nothing in the general mode and arrangement of the enamel-folds, or in the accessory columns, absolutely distinctive between the two principal families, existing species may generally be distinguished, inasmuch as the true molars of the _Cervidæ_ are more or less brachydont, and those of the _Bovidæ_ generally hypsodont, _i.e._, the teeth of the former have comparatively short crowns (Fig. 122), which, as in most mammals, take their place at once with the neck (or point where the crown and root join) on a level with or a little above the alveolar border, and remain in this position throughout the animal’s life; whereas in the other forms (Fig. 123), the crown being lengthened and the root small, the neck does not come up to the alveolar level until a considerable part of the surface has worn away, and the crown of the tooth thus appears for the greater part of the animal’s life partially buried in the socket. In this form of tooth (which is almost always most developed in the posterior molars of the permanent series) the constituent columns of the crown are necessarily nearly parallel, whereas in the first-described they diverge from the neck towards the free or grinding surface of the tooth. In the completely hypsodont form the interstices of the lengthened columnar folds of enamel and dentine are filled up with cement, which gives stability to the whole organ, and is entirely or nearly wanting in the short-crowned teeth. The same modification from low to high crowns without essential alteration of pattern is seen in an even still more marked manner in some of the Perissodactyle Ungulates, the tooth of the Horse bearing to that of _Anchitherium_ the same relation as that of an Ox does to the early selenodont Artiodactyles. A parallel modification has also taken place in the molar teeth of the Proboscidea.

[Illustration: FIG. 123.—Inner and outer aspects of an almost unworn left upper molar of the Nilghai (_Boselaphus tragocamelus_), to show hypsodont type. (From the _Palæontologia Indica_.)]

As the hypsodont tooth is essentially a modification of, and, as it were, an improvement upon, the brachydont, it is but natural to expect that all intermediate forms may be met with. Even among the Deer themselves, as pointed out by Lartet, the most ancient have very short molars, and the depressions on the grinding surface are so shallow that the bottom is always visible; while in the _Cervidæ_ of the more recent Tertiary periods, and especially the Pleistocene and living species, these same cavities are so deep that whatever be the state of the dentition the bottom cannot be seen. Some existing Deer, as the Axis, are far more hypsodont than the majority of the family; and, on the other hand, many of the Antelopes (as _Tragelaphus_) retain much of the brachydont character, which is, however, completely lost in the more modern and highly specialised Sheep and Oxen.

[Illustration: FIG. 124.—Stomach of Ruminant opened to show internal structure. _a_, Œsophagus; _b_, rumen or paunch; _c_, reticulum or honey-comb bag; _d_, psalterium or manyplies; _e_, abomasum or reed; _f_, duodenum.]

The complicated stomach of the Pecora (Fig. 124), which is necessary for the performance of the peculiar function known as “chewing the cud”—a function common also to the Tragulina and Tylopoda—is divided into four well-defined compartments, known as (1) the Rumen or Paunch, (2) the Reticulum or Honey-comb Bag, (3) the Psalterium or Manyplies, (4) the Abomasum or Reed. The paunch is a very capacious receptacle, shaped like a blunted cone bent partly upon itself. Into its broader base opens the œsophagus or gullet at a spot not far removed from its wide orifice of communication with the second stomach or honey-comb bag. Its inner walls are nearly uniformly covered with a pale mucous membrane, which is beset with innumerable close-set, short, and slender villi, resembling very much the “pile” on velvet. The honey-comb bag is very much smaller than the paunch. It is nearly globose in shape, and receives its name on account of the peculiar arrangement of its mucous membrane which forms shallow hexagonal cells all over its inner surface. Running along its upper wall there is a deep groove, coursing from the first to the third stomach. This groove plays an important part in the act of rumination. Its walls are muscular, like those of the viscus with which it is associated, which allows its calibre to be altered. Sometimes it completely closes round so as to become converted into a tube by the opposition of its edges. At others it forms an open canal. The manyplies is globular in form, and its lining membrane is raised into longitudinal folds or laminæ arranged very much like the leaves of a book, and very close together. Their surfaces are roughened by the presence of small projections or papillæ. The reed is the proper digestive stomach, corresponding with the same organ in man. Its shape is somewhat pyriform, and its walls are formed of a smooth mucous membrane, which secretes the gastric juice.

When the food is first swallowed it is conveyed into the paunch, and after undergoing a softening process there it is regurgitated into the mouth, and undergoes a further trituration by the molar teeth and mixture with the secretion of the salivary and buccal glands. It is then swallowed again, but now passes directly through the before-mentioned groove into the manyplies, and, after filtering through the numerous folds of the lining membrane of this cavity, finally reaches the fourth or digestive stomach.

The placenta of the Pecora is characterised by the fœtal villi being collected into groups or cotyledons, which may present either a convex or a concave surface to the uterus. These cotyledons are received into permanent elevations in the mucous membrane of the uterus, the surfaces of which present a curvature which is the reverse of the cotyledons.

_Family_ CERVIDÆ.

Frontal appendages, when present, in the form of antlers. First molar, at least, in both jaws brachydont. Two orifices to the lachrymal duct, situated on or inside the rim of the orbit. An antorbital or lachrymal vacuity of such dimensions as to exclude the lachrymal bone from articulation with the nasal. Upper canines usually present in both sexes and sometimes attaining a very great size in the male (see Fig. 134). Lateral digits of both fore and hind feet, almost always present, and frequently the distal ends of the metapodials. Placenta with few cotyledons. Gall-bladder absent (except in _Moschus_). This family contains numerous species, having a wide geographical distribution, ranging in the New World from the Arctic Circle as far south as Chili, and in the Old World throughout the whole of Europe and Asia, though absent in the Ethiopian and Australian regions.

It may be divided into two subfamilies.

Subfamily =Moschinæ=.—This subfamily is represented solely by the Musk-Deer, which differs so remarkably from the true Deer that it is considered by several writers as the representative of a separate family. The late Professor Garrod even suggested that it should be regarded as an extremely aberrant member of the _Bovidæ_.

[Illustration: FIG. 125.—The Musk-Deer (_Moschus moschiferus_).]

_Moschus._[194]—The Musk-Deer (Fig. 125) in many respects stands by itself as an isolated zoological form, retaining characters belonging to the older and more generalised types of ruminants before they were distinctly separated into the horned and the antlered sections now dominant upon the earth. One of these characters is that both sexes are entirely devoid of any sort of frontal appendage. In this, however, it agrees with one existing genus of true Deer (_Hydropotes_); and, as in that animal, the upper canine teeth of the males are remarkably developed, long, slender, sharp pointed, and gently curved, projecting downwards out of the mouth with the ends turned somewhat backwards. Vertebræ: C 7, D 14, L 5, S 5, C 6. Among the anatomical peculiarities in which it differs from all true Deer and agrees with the _Bovidæ_ is the presence of a gall-bladder. The hemispheres of the brain are but slightly convoluted, and the cotyledons of the placenta are arranged in a peculiar linear manner.[195]

Although, owing to variations of colour presented by different individuals in different localities and seasons, several nominal species have been described, zoologists are now generally agreed that there is but one, the _Moschus moschiferus_ of Linnæus. In size it is rather less than the European Roe Deer, being about 20 inches high at the shoulder. Its limbs, especially the hinder ones, are long. The feet are remarkable for the great development of the lateral pair of hoofs, and for the freedom of motion they all present, so that they appear to have the power of grasping projecting rocky points,—a power which must be of great assistance to the animal in steadying it in its agile bounds among the crags of its native haunts. The ears are large, and the tail quite rudimentary. The hair covering the body is long, coarse, and of a peculiarly brittle and pith-like character, breaking with the application of an extremely slight force; it is generally of a grayish-brown colour, sometimes inclined to yellowish-red, and often variegated with lighter patches. The Musk-Deer has a wide distribution over the highlands of central and eastern Asia, including the greater part of southern Siberia, and extends to Kashmir on the south-west and Cochin-China on the south-east, always, however, at considerable elevations,—being rarely found in summer below 7000 feet above the sea-level, and ranging as high as the limits of the thickets of birch or pines, among which it mostly conceals itself in the daytime. It is a hardy, solitary, and retiring animal, chiefly nocturnal in its habits, and almost always found alone, rarely in pairs, and never in herds. It is exceedingly active and sure-footed, having few equals in traversing rocky and precipitous ground; and it feeds on moss, grass, and leaves of the plants which grow on the mountains among which it makes its home.

Most of the animals of the group to which the Musk-Deer belongs, in fact the large majority of mammals, have some portion of the cutaneous surface peculiarly modified and provided with glands secreting some odorous and oleaginous substance specially characteristic of the species. This, correlated with the extraordinary development of the olfactory organs, appears to offer the principal means by which animals in a state of nature become aware of the presence of other individuals of their own species, or of those inimical to them, even at very great distances, and hence it is of extreme importance both to the well-being of the individual and to the continuance of the race. The situation of this specially modified portion of skin is extremely various, sometimes between the toes, as in Sheep, sometimes on the face in front of the eyes, as in many Deer and Antelopes. Sometimes it is in the form of a simple depression or shallow recess, often very deeply involuted, and in its fullest state of development it forms a distinct pouch or sac with a narrow tubular orifice. In this sac a considerable quantity of the secretion can accumulate until discharged by the action of a compressor muscle which surrounds it. This is the form taken by the special gland of the Musk-Deer, which has made the animal so well known, and has proved the cause of an unremitting persecution to its possessor. It is found in the male only, and is a sac about the size of a very small orange, situated beneath the skin of the abdomen, the orifice being immediately in front of the preputial aperture. The secretion with which the sac is filled is of dark-brown or chocolate colour, and when fresh described as being of the consistence of “moist gingerbread,” but becoming dry and granular after keeping. It has a peculiar and very powerful scent, which when properly diluted and treated forms the basis of many of our most admired perfumes. When the animal is killed the whole gland or “pod” is cut out and dried, and in this form reaches the market of the Western World, chiefly through China.

Subfamily =Cervinæ.=—This subfamily includes all the true Deer. According to the arrangement proposed by Sir V. Brooke[196] the existing _Cervinæ_ may be divided into the sections Plesiometacarpalia and Telemetacarpalia.

=Plesiometacarpalia.=—In this section, which is mainly characteristic of the Old World, the proximal portions of the lateral (second and fifth) metacarpals persist, and the vomer is never so ossified as to divide the posterior osseous nares into two distinct passages. The premaxillæ nearly always articulate with the nasals.

_Cervulus._[197]—Antlers half the length of the head, placed on pedicles nearly equal to them in length. Brow tine short, inclined inwards and upwards; terminal extremity of beam unbranched, and curved downwards and inwards. Lachrymal fossa of skull very large, and extending into facial part of jugal; lachrymal (antorbital) vacuity moderate. Ascending portion of premaxillæ at least as long as nasals. A permanent ridge extending from each pedicle over the orbit, lachrymal fossa and vacuity. Auditory bulla much inflated. Upper canines of males very large. Ectocuneiform united with naviculo-cuboid of tarsus. No traces of the phalanges of the lateral digits.

The native name Muntjac has been generally adopted in European languages for a small group of Deer indigenous to the southern and eastern parts of Asia and the adjacent islands, which are separated by very marked characters from all their allies. They are also called “Kijang” or “Kidjang,” and constitute the genus _Cervulus_ of Blainville and most zoologists;—_Styloceros_ of Hamilton-Smith, and _Prox_ of Ogilby. They are all of small size compared with the majority of Deer, and have long bodies and rather short limbs and neck. The antlers, which as in most Deer are present in the male only, are small and simple, and the main stem or beam, after giving off a very short brow tine, inclines backwards and upwards, is unbranched and pointed, and when fully developed curves inwards and somewhat downwards at the tip. These small antlers are supported upon pedicles or permanent processes of the frontal bones, longer than in any other Deer, and the front edges of which are continued downwards as strong ridges passing along the sides of the face above the orbits, and serving to protect the large supraorbital glands lying on their inner sides. The lachrymal fossa of the skull, in which is lodged the large suborbital gland or crumen, is of great depth and extent. The upper canine teeth of the males are strongly developed and sharp, curving downwards, backwards, and outwards, projecting visibly outside the mouth as tusks, and loosely implanted in their sockets. In the females they are very much smaller. The limbs exhibit several structural peculiarities not found in other Deer. The lateral digits of both fore and hind feet are very little developed, the hoofs alone being present and their bony supports (found in all other Deer) wanting. There is a tufted gland on the outer side of the metatarsus.

The Muntjacs are solitary animals, very rarely even two being seen together. They are fond of hilly ground covered with forests, in the dense thickets of which they pass most of their time, only coming to the skirts of the woods at morning and evening to graze. They carry the head and neck low and the hind-quarters high, their action in running being peculiar and not very elegant, somewhat resembling the pace of a sheep. Though with no power of sustained speed or extensive leap, they are remarkable for flexibility of body and facility of creeping through tangled underwood. They are often called by Indian sportsmen “Barking Deer,” a name given on account of their alarm cry, a kind of short shrill bark, like that of a fox but louder, which may often be heard in the jungles they frequent both by day and by night. When attacked by dogs the males use their sharp canine teeth with great vigour, inflicting upon their opponents deep and even dangerous wounds.

There is some difference of opinion among zoologists as to the number of species of the genus _Cervulus_. Sir Victor Brooke, who investigated this question in 1878 (see _Proceedings of the Zoological Society of London_ for that year, p. 898), came to the conclusion that there are certainly three which are quite well marked, viz.—

_C. muntjac_ (Fig. 126), found in British India, Burma, the Malay Peninsula, Sumatra, Java, Hainan, Banca, and Borneo. The general colour is a bright yellowish-red, darker in the upper parts of the back; the fore legs from the shoulder downwards and the lower part of the hind legs, dark bluish-brown; anterior parts of the face from the muzzle to between the eyes, brown—a blackish line running up the inside of each frontal ridge; chin, throat, inside of hind legs, and under surface of tail white. The female has a black bristly tuft of hair on the spot from which the pedicles of the antlers of the male grow. The average length of the male, according to Jerdon, is 3½ feet, tail 7 inches, height 26 to 28 inches. The female is a little smaller. The specimens from Java, Sumatra, and Borneo are of larger size than those from the mainland, and may possibly be of distinct species or race.

[Illustration: FIG. 126.—The Muntjac (_Cervulus muntjac_).]

_C. lacrymans_ of Milne-Edwards, or Sclater’s Muntjac of Swinhoe, from Moupin, and near Hangchow, China.

_C. reevesi_, a very small species from southern China.

Subsequently the name _C. crinifrons_ has been applied to a Muntjac from Ningpo, China, readily distinguished from all other species by its bushy forehead and long tail. Another species from Tenasserim has been described as _C. feæ_.

Small Deer from the European Pliocene have been provisionally referred to _Cervulus_, but the so-called _Prox furcatus_, of the Miocene, is now included in _Palæomeryx_.

_Elaphodus._[198]—Antlers very small, unbranched, supported on long, slender, converging pedicles. Ascending rami of premaxillæ shorter than nasals. No supraorbital ridges or frontal glands. Upper canines of male long, but not everted. A distinct frontal tuft of hair. Other characters as in _Cervulus_.

This genus (which has also received the name of _Lophotragus_) is represented by a small Deer (Fig. 127) from China of about the same size as the Indian Muntjac. The male has minute simple antlers and very large canine teeth. There are no supraorbital glands, nor is there a tufted gland on the metatarsus. The limbs have the same peculiarities as in _Cervulus_, but the mesocuneiform may also ankylose with the ectocuneiform, and traces of the metacarpals may remain. The hair is coarse and somewhat quill-like.

[Illustration: FIG. 127.—Male of _Elaphodus michianus_. From Sclater _Proc. Zool. Soc._ 1876, p. 273.]

_Cervus._[199]—The great majority of the Deer of the Old World may be included in this large genus, which is one not easy of definition. The antlers of the male are, however, large, and two or three times the length of the head, and may be either rounded or palmate; the canines are never large; the ectocuneiform of the tarsus remains distinct from the naviculo-cuboid; the lateral digits are represented by their phalanges; and the skull does not carry prominent frontal ridges. Vertebræ: C 7, D 13, L 6, S 4, C 11-14. The size of the lachrymal fossa and vacuity, and the degree of inflation of the auditory bulla, are subject to variation in the different groups into which the genus may be divided.

The _Rusine_ group is characteristic of the Oriental region, where it is typically represented by the Sambur (_C. aristotelis_) of India, Burma, and China. The antlers are rounded, and often strongly grooved, without a bez tine, and with the beam simply forked at the extremity, upright, and but slightly curved; the angle formed by the brow tine, which rises close to the burr, being acute. The molars are markedly hypsodont, with small accessory columns. The lachrymal fossa is deep and the vacuity large; the auditory bulla is slightly inflated and rugose. Tail moderate; neck maned.

The Sambur, which is abundant in hilly districts, is a fine animal, standing nearly 5 feet in height, and of massive build; the general colour being deep brown. _C. equinus_, of Borneo, Sumatra, and Singapore, _C. swinhoei_, of Formosa, _C. philippinus_, and _C. alfredi_ of the Philippines, are closely allied species, of which the two latter are of smaller dimensions. The Indian Hog Deer (_C. porcinus_) is a still smaller form, not larger than the Roe. _C. hippelaphus_ of Java, _C. timoriensis_, and _C. moluccensis_ are distinguished by the posterior branch of the beam of the antler being considerably larger than the anterior.

The _Rucervine_ group is another strictly Oriental one, and is represented by the Swamp Deer (_C. duvaucelli_) of India, the closely allied _C. schomburgki_ of Siam, of which the antlers are shown in Fig. 119 (p. 309), and _C. eldi_ of Burma and Hainan. The beam of the antler is somewhat flattened, and more curved than in the Rusine group; the large brow tine is given off from the beam at an obtuse angle and curves upwards; the beam bifurcates into two branches, which again divide. Skull as in the Rusine group, but relatively narrower. Tail short; neck maned.

The Swamp Deer is somewhat smaller than the Sambur, and of a full yellowish colour. Fossil representatives of this group occur in the Pliocene of India.

The _Elaphurine_ group is represented only by the very aberrant _C. davidianus_ of Northern China. In size and proportions this species approximates to the Swamp Deer, but the antlers are peculiar in rising straight from the brow and then giving off a long and straight back tine (correlated by Sir V. Brooke with the posterior branch of the Rusine antler); the summit of the beam is forked, and in old individuals the two tines of the fork may again branch. Nasals long, and much expanded between the lachrymal vacuities, of which they form the inner border; lachrymal fossa large and deep. Tail long; neck maned.

The _Axine_ group includes only the well-known Axis of India, readily distinguished by the white spots with which the body is marked. Antlers of a Rusine type, the beam being much curved, and the brow tine usually given off at an acute or right angle. Molars very hypsodont. The coloration of the Axis is more brilliant than that of any other member of the family.

Here may be noticed a group of Deer mainly characteristic of the eastern Palæarctic region, frequently known as the _Pseudaxine_ group, which appears to connect the Axine with the Elaphine type. Well-known representatives of this group are _C. sika_ (Fig. 128) of Japan, _C. mantchuricus_ of China, and _C. taëvanus_ of Formosa. The antlers have a brow and tres tine, and then a forked beam, of which the posterior tine is the smaller. The lachrymal vacuity and fossa are of moderate size; and the auditory bulla is only moderately inflated, and quite smooth externally. Tail moderate; neck maned. In summer the coat is spotted, but is plain in winter. A herd of _C. sika_ have been acclimatised in Ireland by Viscount Powerscourt, at Powerscourt, County Wicklow. A number of Deer from the Pliocene of Europe, such as _C. perrieri_ and _C. etueriarum_, appear to be allied both to the Pseudaxine and Axine groups.

[Illustration: FIG. 128.—The Japanese Deer (_Cervus sika_). From Lord Powerscourt, _Proc. Zool. Soc._ 1884, p. 209.]

The _Elaphine_ or typical group is at once characterised by the presence of a bez tine to the antlers (Fig. 129), in which the beam is rounded, and splits up near the summit into a larger or smaller number of snags, often arranged in a cup-like manner. Skull as in the preceding group. All the species large. The Red Deer, _C. elaphus_, which is dark brown in colour, with a light patch on the rump, inhabits Europe, Western Asia, and Northern Africa—the so-called Barbary Deer not being specifically distinct. A full-grown Scotch Stag is fully 4 feet in height at the withers. The antlers are shed between the end of February and the early part of April; old animals shedding earlier than younger ones. The young, which (as in all the members of the genus except some of the Rusine species) are spotted, are born at the end of May or the beginning of June. The points on the antlers increase in number with the age of the creature, and when twelve are present it is known in Scotland as a “royal stag.” This number, however, is sometimes exceeded, as in the case of a pair of antlers, weighing 74 lbs., from a stag killed in Transylvania, which had forty-five points. The antlers during the second year consist of a simple unbranched stem, to which a tine or branch is added in each succeeding year, until the normal development is attained, after which their growth is somewhat irregular. Many of the antlers dug up in British peat-beds (as Fig. 118) are larger than those of living individuals, and in the cave-deposits of England and the Continent antlers are met with rivalling those of the Wapiti in size; these large fossil antlers probably indicating the ancestral form from which the Red Deer and several of the allied species are descended.

[Illustration: FIG. 129.—Head of the Wapiti (_Cervus canadensis_).]

The North American Wapiti (_Cervus canadensis_, Fig. 129), the Persian Maral (_C. maral_), the Kashmir Stag (_C. cashmeerianus_), as well as _C. affinis_ of Tibet, are all closely allied to the Red Deer, but are of larger size, this being especially the case with the first two. A fine example of the antlers of the Wapiti is shown in the accompanying woodcut, and exhibits the absence of a cup at the surroyals, by which this species is distinguished from the Red Deer.

The last, or _Damine_ group of existing Deer includes the Common and the Persian Fallow Deer. These are readily characterised by the palmation of the antlers in the region of the surroyals and the spotted coat. The Common Fallow Deer (_C. dama_) stands about three feet in height. The Persian Fallow Deer (_C. mesopotamicus_) is very closely allied, differing only in its slightly larger size and the form of the antlers, the two breeding together. The common species, although now kept in English parks, does not appear to be a native of this country, having probably been introduced from the regions bordering the Mediterranean. The fur is of a yellowish-brown colour (whence the name “fallow”), marked with white spots; there is, however, a uniformly dark brown variety found in Britain. The bucks and does live apart, except during the pairing season; and the doe produces one or two, and sometimes three fawns at a birth. The Fallow Deer from the Pleistocene and Pliocene deposits of the East Coast described under the names of _C. browni_ and _C. falconeri_ appear to have been closely allied to the existing species. The remarkable _C. verticornis_, of the Norfolk Forest-bed, is regarded as an aberrant member of this group, in which the antlers are very short and thick, with the brow tine cylindrical and downwardly curved, and the beam expanded above the tres tine into a crown with two points.

The extinct Irish Deer (_Cervus giganteus_), of which the skeleton is shown in the woodcut (Fig. 130), is the only representative of the _Megacerotine_ group. The antlers, which may have a span of over 11 feet, are enormously palmated, and have a bifurcated brow tine, a small bez tine, and a third posterior tine. The skeleton measures upwards of 6 feet at the withers. Remains of this species are especially common in the peat-bogs of Ireland, but are also met with in Pleistocene deposits over a large part of Europe. In addition to the forms already mentioned there are many other fossil species of _Cervus_, some of which, like the English Pleistocene _C. sedgewicki_, cannot be included in any of the existing groups. There is no conclusive evidence of the existence of any species of _Cervus_ before the Lower Pliocene period.

=Telemetacarpalia.=—This section includes all the Deer of the New World, together with some Old World forms, and is characterised by retaining the distal extremities of the lateral (second and fifth) metacarpals. With the exception of _Alces_, _Capreolus_, and _Hydropotes_ (which are either partly or entirely Old World types), the vomer is so much ossified as to divide the posterior bony nares into two distinct orifices (Fig. 132).

[Illustration: FIG. 130.—Skeleton of the Gigantic Irish Deer (_Cervus giganteus_). After Owen.]

_Rangifer._[200]—The Reindeer, or Caribou as it is termed in North America, is the sole representative of the genus _Rangifer_, which is sufficiently distinguished from all its allies by the presence of antlers in both sexes. The lachrymal vacuity is small. This animal is distributed over the northern parts of Europe, Asia, and America; the differences which may be observable in specimens from different regions not being sufficient to allow of specific distinction. The Reindeer is a heavily built animal, with short limbs, in which the lateral hoofs are well developed, and the cleft between the two main hoofs is very deep, so that these hoofs spread out as the animal traverses the snow-clad regions in which it dwells. The antlers (Fig. 131) are of very large relative size. There is a bez as well as a brow tine, which are peculiar in being either branched or palmated. In the American race (Caribou), as well as in some of the specimens found fossil in the English Pleistocene (Fig. 131), one of the brow tines is generally aborted to allow of the great development of the other. The dentition of the Reindeer is frequently remarkable for the very small size of the posterior lobe of the last lower molar. Vertebræ: C 7, D 14, L 5, S 5, C 11.

[Illustration: FIG. 131.—Skull and antlers of the Reindeer (_Rangifer tarandus_), from an English Pleistocene deposit. _br_, Brow tine; _bz_, bez tine. (After Owen.)]

The Reindeer has long been domesticated in Scandinavia, and is of especial value to the Laplanders, whom it serves as a substitute for the Horse, Cow, Sheep, and Goat. It is capable of drawing a weight of 300 lbs., and its fleetness and endurance are remarkable. Harnessed to a sledge it will travel without difficulty 100 miles a day over the frozen snow, on which its broad and deeply cleft hoofs are admirably adapted for travelling. During the summer the Lapland Reindeer feeds chiefly on the young shoots of the willow and birch; and since at this season migration to the coast seems necessary to the well-being of this animal, the Laplander, with his herds, sojourns for several months in the neighbourhood of the sea. In winter its food consists chiefly of the so-called reindeer-moss and other lichens which the animal makes use of its hoofs in seeking for beneath the snow. The wild Reindeer grows to a much greater size than the tame breed; but in Northern Europe the former are being gradually reduced through the natives entrapping and domesticating them. The tame breed found in Northern Asia is much larger than the Lapland form, and is there used to ride on. Remains referable to the existing species are found in the cavern and other Pleistocene deposits of Europe.

[Illustration: FIG. 132.—Hinder part of the base of the cranium of the Virginian Deer (_Cariacus virginianus_). From Garrod, _Proc. Zool. Soc._ 1877, p. 13.]

_Alces._[201]—The Elk or Moose (_Alces machlis_) has the same general distribution as the Reindeer, and is likewise the single existing representative of its genus. It is the largest existing member of the family, attaining sometimes a height of 8 feet at the withers. The antlers (Fig. 133) have neither brow nor bez tine, but form an enormous basin-shaped palmation, primarily composed of an anterior and a posterior branch; their weight may be as much as 60 lbs. The nasal bones are very short, and the narial aperture of great size. The Elk is covered with a thick coarse fur of a brownish colour, longest on the neck and throat. Its legs are long and its neck short, and as it is thus unable to feed close to the ground, it browses on the tops of low plants, the leaves of trees, and the tender shoots of the willow and birch. Its antlers attain their full length by the fifth year, but in after years they increase in breadth and in the number of snags, until fourteen of these are produced. Although spending a large part of their lives in forests, Elks do not suffer much inconvenience from the great expanse of their antlers, as in making their way among trees they are carried horizontally to prevent entanglement with the branches. Their usual pace is a shambling trot, but when frightened they break into a gallop. The natural timidity of the Elk forsakes the male at the rutting season, and he will then attack whatever animal comes in his way. The antlers and hoofs are his principal weapons, and with a single blow from the latter he has been known to kill a wolf. The female often gives birth to two fawns, and with these she retires into the deepest recesses of the forest, the young remaining with her till their third year. The Elk ranges, but in scanty numbers, over the whole of Northern Europe and Asia, as far south as East Prussia, the Caucasus, and North China, and over North America from the New England States westward to British Columbia. Fossil species are found in the Pleistocene deposits of Europe.

_Cervalces._[202]—A remarkable extinct Deer from the Pleistocene of North America, described as _Cervalces_, appears in some respects (although a true Telemetacarpalian) to connect _Alces_ with _Cervus_. Thus the palmated antlers are divided into anterior and posterior branches, but below this division there are two tines apparently corresponding to the bez and posterior tines of _Cervus giganteus_ (Fig. 130).

[Illustration: FIG. 133.—Head of Elk (_Alces machlis_).]

_Capreolus._[203]—Antlers (in the existing species) less than twice the length of the head, usually with three tines on each. Brow tine developed from the anterior surface of the upper half of the antler, and directed upwards. Lachrymal vacuity small. Premaxillæ not always articulating with nasals. Auditory bullæ slightly inflated, rugose externally. Vertebræ: C 7, D 13, L 6, S 6, C 8. Tail very short. Glands in fore feet rudimentary; large in hind feet.

The Roe, or Roe Deer (_Capreolus caprea_), is a small form distributed over Europe and Western Asia, being one of the species found in the British Isles. The male is somewhat over two feet in height at the withers, of a dark reddish-brown colour in summer, with a white patch on the rump. The small antlers are approximated at their bases, and consist of a rugged beam rising vertically for some distance, then bifurcating, and the posterior branch again dividing. The Roe dates from the Pleistocene period. Extinct Deer from the Continental Pliocene have been provisionally referred to _Capreolus_.

_Hydropotes._[204]—No antlers in either sex. Lachrymal fossa deep and short (Fig. 134); lachrymal vacuity of moderate size. Orbits small and but slightly prominent. Auditory bulla much inflated. Angle of mandible much produced backwardly (Fig. 134); alveolar margins of mandible in diastema sharp and everted. Canines of male very large, and slightly convergent. Vertebræ: C 7, D 12, L 6, S 4, C 10. No tufts on metatarsals. Foot glands small in fore feet, deep in hind ones.

[Illustration: FIG. 134.—The left lateral view of the skull of a male Chinese Water Deer (_Hydropotes inermis_), with the wall of the maxilla cut away to show the root of the canine. ½ natural size. (From Sir V. Brooke, _Proc. Zool. Soc._ 1872, p. 524.)]

[Illustration: FIG. 135.—Upper surface of the brain of _Hydropotes inermis_. (From Garrod, _Proc. Zool. Soc._ 1877, p. 792.)]

The Chinese Water Deer (_H. inermis_) is the sole representative of this genus. In the absence of antlers and the large canines of the male it resembles _Moschus_, although very different in other respects. Thus the brain (Fig. 135) has the hemispheres much convoluted, as in other _Cervinæ_, and approximates to that of _Pudua_; while the placenta and viscera likewise agree with those of the true Deer. In the total absence of any ossification of the vomer to divide the posterior nares _Hydropotes_ resembles _Capreolus_ and differs from all the following genera. The Chinese Water-Deer is nearly of the same size as the Indian Muntjac. It has short legs and a long body, the hair covering the latter being of a light reddish-brown. It is a remarkably prolific animal, differing from all other Deer in producing five or six young at a time.

The mandible of a ruminant from the Middle Miocene of Gers in France, described under the name of _Platyprosopus_, presents such a marked resemblance to _Hydropotes_ in the form of the angle as to suggest a more or less intimate affinity.

_Cariacus._[205]—Skull (Fig. 132) with the vomer dividing the posterior nares into two distinct chambers; premaxillæ not reaching nasals. Antlers never greatly exceeding the length of the head. Lachrymal vacuity very large, and lachrymal fossa small. Auditory bullæ slightly inflated. Vertebræ: C 7, D 13, L 6, S 4, C 13. Tail long or short. Colour uniform in adult.

This genus, which agrees with the Reindeer in the division of the posterior nares by the ossified vomer, comprises a number of species confined to the New World, none of which attain very large dimensions, and the antlers of which are relatively smaller than in the existing species of _Cervus_. The genus may be divided into groups.

The typical _Cariacine_ group, as represented by _C. virginianus_, has well-developed antlers, with a short brow tine rising from the inner side of the beam, and directed upwards, and several branches; a long tail; and no upper canines. In this species, as well as in _C. mexicanus_ and other forms, the antlers do not divide dichotomously, and the lachrymal fossa is of moderate depth. The Mule Deer (_C. macrotis_) of North America is distinguished by the dichotomous branching of the antlers and the deeper lachrymal fossa. The Virginian Deer is somewhat smaller than the Fallow Deer, and of a uniform reddish-yellow colour in summer, and light gray in winter.

The _Blastocerine_ group of South America is represented by _C. paludosus_ and _C. campestris_, and has dichotomous antlers, with no brow tine, and the posterior branch the larger, a short tail, and no upper canines. The _Furciferine_ group includes _C. chilensis_ and _C. antisiensis_, confined to western South America. The antlers are not longer than the head, with a large anterior tine curving forwards at right angles to the simple posterior one. Auditory bullæ slightly inflated, and rugose. Upper canines may be present. The species are of medium size. _C. clavatus_, of Central America, while resembling this group in the characters of the skull and the arrangement of the hair on the face, agrees with the next one in having simple spike-like antlers.

The South American _Coassine_ group comprises the small forms known as Brockets, in which the antlers form simple spikes not exceeding half the length of the head. Some six species are known.

Remains of _Cariacus_, mostly or entirely referable to existing species, are of common occurrence in the Brazilian cave-deposits. _Blastomeryx_, of the Pliocene of North America, is believed to be an allied type.

_Pudua._[206]—Antlers in the form of minute simple spikes. Distinguished from the Coassine group of _Cariacus_ by the articulation of the premaxillæ with the nasals (as in the _Furciferine_ group), and the coalescence of the ectocuneiform with the naviculo-cuboid, as well as by various external characters. No upper canines. Represented only by the very small _P. humilis_ of the Chilian Andes.

_Extinct Genera._—In the European and other Tertiary deposits several genera of extinct _Cervidæ_ occur, of which the more important may be briefly mentioned. _Amphitragulus_, of the Lower Miocene of the Continent, has four lower premolars, brachydont molars, and no antlers; the largest species being somewhat bigger than the Musk-Deer. The closely allied _Palæomeryx_ (_Dremotherium_ or _Micromeryx_) generally has but three lower premolars, and the brachydont upper molars (Fig. 122), like those of _Amphitragulus_, want the small accessory inner column[207] found in modern Deer. In _P. feignouxi_, of the Lower Miocene, the lateral metacarpals, although slender, were complete, and the males had large canines, but no antlers. _P. furcatus_, of the Middle Miocene, had small antlers, and the canines appear to have been reduced in size. This genus, besides being represented in the European Miocene, also occurs in the Pliocene of India and China; some of the species being as large as the Red Deer.

_Family_ GIRAFFIDÆ.

In the existing genus the frontal appendages consist of a pair of short, erect, permanent bony processes placed over the union of the frontal and the parietal bones, ossified from distinct centres, though afterwards ankylosed to the skull, covered externally with a hairy skin, present in both sexes, and even in the new-born animal. Anterior to these is a median protuberance on the frontal and contiguous parts of the nasal bones, which increases with age, and is sometimes spoken of as a third horn. Skull with a lachrymal vacuity. No upper canines. Molars brachydont, with rugose enamel; the upper ones having no inner accessory column. Lateral digits entirely absent on both fore and hind feet, even the hoofs not developed. Humerus with double bicipital groove. Vertebræ: C 7, D 14, L 5, S 3, C 20. Gall-bladder generally absent. Male reproductive organs and placenta of a Bovine type. Dentition: _i_ ⁰⁄₃, _c_ ⁰⁄₁, _p_ ³⁄₃, _m_ ³⁄₃.

[Illustration: FIG. 136.—The Giraffe (_Giraffa camelopardalis_).]

_Giraffa._[208]—The Giraffe (_G. camelopardalis_) is the sole existing representative of the genus, now confined to the Ethiopian region.

In addition to the characters noticed above, the Giraffe is characterised by its great size and peculiar proportions; the neck and limbs being of great length, and the back inclining upwards from the loins to the withers.

To produce the extremely elongated neck the seven cervical vertebræ are proportionately long, which gives a somewhat stiff and awkward motion to the neck. The ears are large, the lips long and thin, the nostrils closable at the will of the animal, the tongue very long and extensile, and the tail of considerable length, with a large terminal tuft. An adult male may have a total height of 16 feet. The coloration consists of large blotches of darker or lighter chestnut-brown on a paler ground, the lower limbs and under parts being of a uniform pale colour. The Giraffe feeds almost exclusively on the foliage of trees, showing a preference for certain varieties of mimosa, and for the young shoots of the prickly acacia, for browsing on which its prehensile tongue and large free lips are specially adapted. It is gregarious in its habits, living in small herds of about twenty individuals, although Sir S. Baker, who hunted it in Abyssinia, states that he has seen as many as a hundred together.

Fossil species of _Giraffa_ occur in Pliocene deposits over Greece, Persia, India, and China, thus affording one of many striking instances of the former wide distribution of the generic types now confined to the Ethiopian region.

_Allied Extinct Types._—The Pliocene deposits of many parts of the Old World yield remains of a number of large Ruminants which show such evident signs of affinity with the Giraffe that it is difficult to draw up a definition by which they can be separated in characters of family value from that genus. On the other hand, some of these forms approximate in the characters of the skull to some of the brachydont members of the _Bovidæ_, although it is quite clear from the nature of the cranial appendages that they cannot be included in that family. All these forms have brachydont molars, with rugose enamel, like those of the Giraffe; while several of them have limb-bones approximating to those of the latter—the humerus, when known, having a double bicipital groove. The nature of the cranial appendages (when present) is not fully understood, but it appears that in some cases these approximated more to the type of an antler than to that of a horn; although, from the absence of a “burr,” they appear never to have been shed. A gradual diminution in the length of the limbs and neck can be traced from the more Giraffoid to the more Bovoid forms of this extinct group; and it is manifest that if these animals be included in the _Giraffidæ_ the definition of that family as given above must be somewhat modified. Only brief mention can be made of the more important genera.

The imperfectly known _Vishnutherium_, of the Pliocene of India and Burma, seems to make the nearest approach to the Giraffe, but the limbs and cervical vertebræ were decidedly shorter, although of a similar slender type. _Helladotherium_, of the Pliocene of Greece and India, is represented by a species of considerably larger size than the Giraffe, with no appendages or lachrymal vacuity to the skull, and with shorter and stouter limbs and neck.

_Hydaspitherium_, _Bramatherium_, and _Sivatherium_ are Indian genera, characterised by the presence of large palmated and antler-like cranial appendages, varying considerably in arrangement. The former genus has a large lachrymal vacuity which is absent in the two latter. In the first and second genera all the appendages rise from a common base; but in _Sivatherium_ there is a pair of simple horn-like projections on the orbits in addition to the posterior palmated antlers. _Sivatherium_ was an animal of huge bulk, being the largest known representative of the Pecora.

Another apparently allied type is _Samotherium_, of the Pliocene of the Isle of Samos, which appears also to have some affinity with the Antelopes. The skull is nearly as large as that of the Giraffe, and is of the same elongated shape, although depressed between the conical horn-cores, which rise vertically above the orbits, and without a median bony prominence on the frontals. The horn-cores form mere processes of the frontals. The diastema and the mandibular symphysis are shorter than in the Giraffe, and the latter is less deflected. The teeth, although larger, are almost indistinguishable from those of the Giraffe, the only well-marked difference being that the last lower premolar has a double in place of a single postero-internal column.

_Family_ ANTILOCAPRIDÆ.

Closely allied to the _Bovidæ_, but the horns deciduous and branched.

_Antilocapra._[209]—The Prong-buck, or Prong-horned Antelope (_Antilocapra americana_), as the single existing member of this family is called, is an animal of nearly the same size as the Fallow Deer, but of a lighter and more graceful build. It is an inhabitant of the prairies of North America, where it is one of the few representatives of the Cavicorn Pecora. The bony horn-cores are unbranched, and form vertical, blade-like projections immediately above the orbit. The horns themselves are compressed, and nearly one foot in length, having a gentle backward curvature, the short branch arising somewhat above the middle of its height, and inclining forwards. When the horn is about to be cast off it becomes loosened, and a new one is formed upon the bony core beneath it. The ears are long and pointed, and the tail is short. The neck has a thick mane of long chestnut-coloured hair, and there is a white patch on the rump.

_Family_ BOVIDÆ.

Frontal appendages, when present, in the form of non-deciduous horns. Molars frequently hypsodont. Usually only one orifice to the lachrymal canal, situated inside the rim of the orbit. Lachrymal bone almost always articulating with the nasal. Canines absent in both sexes. The lateral toes may be completely absent, but more often they are represented by the hoofs alone, supported sometimes by a very rudimentary skeleton, consisting of mere irregular nodules of bone. Distal ends of the lateral metapodials never present. Gall-bladder almost always present. The number of cotyledons in the placenta generally varies from 60 to 100; whereas in the _Cervidæ_ the number is usually from 5 to 12, _Capreolus_ and _Hydropotes_ having the fewest. In _Giraffa_ the number is upwards of 180. The nature of the horns and horn-cores has been already explained; in the majority of genera these appendages are present in both sexes, although much larger in the male (see p. 310).

The _Bovidæ_, or hollow-horned Ruminants (Cavicornia), form a most extensive family, with members widely distributed throughout the Old World, with the exception of the Australian region; but in America they are less numerous, and confined to the Arctic and northern temperate regions, no species being indigenous either to South or Central America. There is scarcely any natural and well-defined group in the whole class which presents greater difficulties of subdivision than this; consequently zoologists are as yet very little agreed as to the extent and boundaries of the genera into which it should be divided. For the present the genera provisionally adopted may be arranged under a number of sections or groups, which some writers regard as subfamilies. The series may be commenced with the Antelopes, the greater number of which are now characteristic of the Ethiopian region.

_Alcelaphine Section._—Includes large African Antelopes, of which the type genus ranges into Syria; generally characterised by their great height at the withers as compared with the rump. Skull with large frontal sinuses, extending into the horn-cores, and the horns lyre-shaped or recurved, and more or less approximated at the base. No large pits at apertures of supraorbital foramina in frontals; upper molars hypsodont and narrow. Horns in both sexes. General colour mostly uniform.

_Alcelaphus._[210]—If _Damalis_ be included, this genus is represented by some nine or ten living species. Head more or less long and narrow, with the muffle moderately broad and naked. Nostrils approximated, edged with stiff hairs. Horns compressed and ringed at the base, more or less lyrate, and bent back at the tips. Hoofs small. Tail of moderate length, and heavy. Two mammæ.

[Illustration: FIG. 137.—The Harte-beest (_Alcelaphus caama_).]

In the typical forms, such as the Bubaline Antelope (_A. bubalinus_), the Harte-beest (_A. caama_, Fig. 137), and the Tora Antelope (_A. tora_, Fig. 138), the horns, which present the peculiar curvature shown in the figures, are situated on a crest at the vertex of the skull, and the facial portion of the cranium is greatly elongated. The Harte-beest, which is found throughout Central and Southern Africa, stands nearly 5 feet high at the withers, and is a somewhat ungainly looking animal, with short hair, which is grayish-brown above and nearly white beneath. In the Pliocene of the Siwalik Hills in Northern India there occur remains of an _Alcelaphus_ (_A. palæindicus_) in which the skull had the long facial portion characteristic of the typical group, while the horns approximate to those of the Bontebok. The Blessbok (_A. albifrons_) and Bontebok (_A. pygargus_), belonging to the genus _Damalis_ of many authors, have the facial portion of the skull shorter, the horns situated more in advance of the plane of the occiput, and inclining regularly backwards. Of the Blessbok Mr. C. J. Anderson observes that “it is of a beautiful violet colour, and is found in company with black Wildebeests and Springboks in countless thousands on the vast green plains of short crisp, sour grass occupying a central position in South Africa. Cattle and horses refuse to pasture on the grassy products of these plains, which afford sustenance to myriads of this Antelope, whose skin emits a most delicious and powerful perfume of flowers and sweet-smelling herbs.” Since the time this was written these Antelopes have been greatly reduced in number. _A. (Damalis) hunteri_, from East Africa, appears to be allied to _A. senegalensis_, but in the more elongated facial portion of the skull approximates to the Harte-beest, and thus confirms the view that _Damalis_ should not form a distinct genus.

[Illustration: FIG. 138.—Head of _Alcelaphus tora_. From Sclater, _Proc. Zool. Soc._ 1873, p. 762.]

_Connochætes._[211]—Head short and massive, with the muffle very broad and bristly. Nostrils widely separated, hairy within. Horns on the vertex of the skull, immediately over the occiput, approximated at base, cylindrical, bent outwards, and recurving upwards at the tip. Extremities of premaxillæ much expanded laterally, and firmly ankylosed. Vertebræ: C 7, D 14, L 6, S 4, C 16. Hoofs very narrow. Tail very long, covered throughout with long hairs. Four mammæ. Two species, _C. taurina_ and _C. gnu_ (Fig. 139), both from South Africa. The former, or Brindled Gnu, is distinguished by the absence of long hair on the face, the black (instead of white) tail, and the presence of dark vertical streaks on the shoulders; it is never found to the south of the Orange River.

The White-tailed Gnu stands about 4 feet 6 inches at the withers. These animals were formerly found in large herds, and are remarkable not only on account of their peculiar form, but also for their grotesque actions when alarmed. Some interesting observations have recently been published upon the mode of development of the horns of the Gnu,[212] from which it appears that in very young individuals the horns are straight and divergent, situated some distance below the vertex of the head, and separated by a wide hairy interval. These young horns form the straight tips of those of the adult, the basal downwardly curved portion being subsequently developed. In the fully adult animal the base of the horns forms a helmet-like mass on the forehead which completely obliterates the hairy frontal space of the young.

[Illustration: FIG. 139.—The White-tailed Gnu (_Connochætes gnu_).]

_Cephalophine Section._—Small or medium-sized African and Indian Antelopes, with simple horns present only in the males, a more or less elongated suborbital gland, a lachrymal depression in the skull, and square-crowned upper molars (Fig. 140). Lateral hoofs well developed.

_Cephalophus._[213]—One pair of horns, arising far back on the frontals, conical, short, angulated at the base, and erect or recurved. Suborbital gland opening in the form of a slit, or as a row of pores. Auditory bulla divided by a distinct septum. Muffle large and moist. Tail very short. Head tufted. Upper molars of larger species with an accessory internal column. Dorsal vertebræ fourteen in number. Some sixteen species, confined to southern and tropical Africa.

The Duikerboks, as the members of this genus are called, are among the most graceful of the African Antelopes, the smallest species not being larger than a rabbit. The West African _C. sylvicultor_ and _C. longiceps_ are the largest species.

_Tetraceros._[214]—Two pairs of conical horns, of which the anterior are much the smaller. Suborbital gland elongated, and lachrymal fossa very large. Upper molars (Fig. 140) without accessory internal column. One existing Indian species (_T. quadricornis_).

[Illustration: FIG. 140.—Palatal and outer aspects of the three right upper premolars and first molar of the Four-horned Antelope (_Tetraceros quadricornis_). From the _Palæontologia Indica_.]

The Four-horned Antelope is found throughout the peninsula of India in jungle. The general colour is brown, lighter beneath and on the inside of the limbs. Remains of this species are found fossil in the cave-deposits of Madras, and a small Ruminant from the Pliocene of the Siwalik Hills has been provisionally referred to this genus.

_Cervicaprine Section._—Small or large Antelopes now confined to the Ethiopian region, with horns present only in the males, lachrymal vacuity generally large, more or less distinct pits at the apertures of the supraorbital foramina in the frontals, and narrow upper molars in which there is no accessory internal column.

_Neotragus._[215]—Distinguished from the next genus by having the crown of the head tufted, muzzle hairy, premaxillæ long and reaching the lachrymals, nasals very short, mesethmoid much ossified, third lobe of last lower molar either absent or very small, and the hinder lobe of the corresponding upper molar much reduced.

Three species, Salt’s Antelope (_N. saltianus_), from Abyssinia, and also _N. kirki_ and _N. damarensis_; the two latter having a small third lobe to the last molar. Writing of the first-named species, Mr. W. T. Blanford[216] observes that “the _Beni-Israel_, or _Om-dig-dig_, one of the smallest Antelopes known, abounds on the shores of the Red Sea and throughout the tropical and subtropical regions of Abyssinia. It is occasionally, but rarely, found at higher elevations; I heard of instances of its being shot both at Serafie and Dildi, but it is not often seen above about 6000 feet. It inhabits bushes, keeping much to heavy jungle on the banks of water-courses, and is usually single, or in pairs, either a male and female or a female and young being found together; less often the female is accompanied by two young ones, which remain with her until full grown.”

_Nanotragus._[217]—Horns small, parallel with frontals, and rising immediately above postorbital process of frontals, in front of the fronto-parietal suture. Lachrymal fossa very large, suddenly descending in front of the orbit, and extending on to the maxilla; lachrymal vacuity small. Auditory bulla large and smooth, without internal septum. Nasals of moderate length. Crown of the head smooth; naked part of muffle small; aperture of suborbital gland small. Lateral hoofs small or absent. Nine species.[218]

The typical species is the Royal Antelope (_N. pygmæus_) of Guinea, the smallest existing representative of the Pecora. This species, together with _N. moschatus_ and _N. tragulus_ have no lateral hoofs, or tufts on the knees. In the _Scopophorine_ group, comprising _N. scoparia_, _N. montanus_, and _N. hastatus_, both these appendages are present; while in the _Oreotragine_ group (_N. melanotis_ and _N. oreotragus_) the former are present and the latter absent.

_Pelea._[219]—Horns rather small, compressed, upright, scarcely diverging, and placed immediately over the orbits. No suborbital gland, nor lachrymal fossa; premaxillæ not reaching nasals. Tail short and bushy. Colour uniform. One species—the Rehbok (_P. capreola_), South Africa, is nearly of the size of a Fallow Deer, although more resembling a Chamois in build and habits. The colour is of a uniform light gray. This animal inhabits bare rocky districts, and thus differs widely from the Water-buck and its allies.

_Cobus._[220]—Large Antelopes, with the horns large, elongate, sublyrate, and ringed at the base, and with rudimentary suborbital glands. Skull with a deep frontal hollow, no lachrymal depression, large lachrymal vacuity, and the premaxillæ reaching the very long nasals. Tail long, with a ridge of hair above, and slightly tufted at the end. Colour uniform. Six species, African.

The Antelopes of this genus are water-loving animals, the Water-buck (_C. ellipsiprymnus_) and the Singsing (_C. defassus_) being well-known examples. Both these species are much alike, standing as much as 4 feet 6 inches at the withers. The Water-buck of South and Eastern Africa is characterised by the coarseness of its long hair; while in the Singsing of West and Central Africa the hair is remarkably fine and soft. Fossil Antelopes from the Pliocene of India are referred to _Cobus_. _Helicophora_, from the Lower Pliocene of Attica, is regarded as allied to _Cobus_, but it has no distinct supraorbital pits.

_Cervicapra._[221]—An allied South African genus in which the tail is short and bushy and the premaxillæ do not reach the nasals. Three species.

The Reitbok (_C. arundineum_) is of a grizzly ochre colour; it stands nearly 3 feet in height, and has horns about 1 foot in length. The Nagor (_C. redunca_) is about 6 inches shorter, with horns of half the length, and fulvous brown above and white below; the West African _C. bohor_ being rather larger.

_Antilopine Section._—A large group of moderate-sized or small Antelopes, most abundant in the deserts bordering the Palæarctic, Oriental, and Ethiopian regions. Horns generally compressed and lyrate, or recurved, or cylindrical and spiral, ringed at base, sometimes present in both sexes. Skull with large pits at apertures of supraorbital foramina of frontals, and generally a distinct lachrymal fossa. Molars of upper jaw narrow, without inner accessory column, and resembling those of the Sheep and Goats. Tail moderate, compressed, hairy above.

_Antilope._[222]—Horns, present only in the male, long, cylindrical, subspiral, and diverging. Suborbital gland large, with a somewhat linear opening; lachrymal depression of skull very large, and a small lachrymal fissure. Glands in the feet; lateral hoofs present. One species, India.

The well-known Black-buck (_A. cervicapra_) is found on open plains all over India, except in lower Bengal and Malabar. Old males are deep blackish-brown in colour on the back and sides and the outer surfaces of the limbs, the under parts and inner surfaces of the limbs white, and the back of the head, nape, and neck yellowish. Young males and females are fawn-coloured above. Very large herds are seen in the plains about Delhi and Mattra, which are said in some instances to reach to thousands. Horn-cores are found in the Pleistocene deposits of the valley of the Jumna which cannot be distinguished from those of the existing species.

_Æpyceros._[223]—Horns compressed, lyrate, and wide-spreading; present only in male. No suborbital gland, or lachrymal depression in the skull. No lateral hoofs. Two species; one from South and the other from West Africa.

The Palla (_Æ. melampus_) is a large Antelope standing over 3 feet high at the withers, and readily distinguished by its dark red colour, gradually shading to white below. It is usually found on or near hills in herds of from twenty to thirty. _Æ. petersi_ is from the Congo.

_Saiga._[224]—Nose very large, convex, and inflated. Supraorbital gland present. Lachrymal fossa of skull small, and fissure absent; narial aperture very large; nasals extremely short; supraorbital pits rather small. Horns yellow, lyrate, of moderate length; present only in male. Vertebræ: C 7, D 13, L 6, S 4, C 10. One species, Eastern Europe and Western Asia.

The Saiga (_S. tatarica_) is a clumsily built and somewhat sheep-like Antelope inhabiting the steppes; it occurs fossil in the Pleistocene of France and England.

_Pantholops._[225]—Allied in the characters of the head and skull to _Saiga_, but the nose less convex, the nostrils of the male more swollen, and the horns of that sex black, very long, compressed, and lyrate; those of female very short. One species, Central Asia.

The Chiru (_P. hodgsoni_) inhabits the highlands of Western Tibet and Turkestan. In the former area it generally goes in small herds of from three to six, and in the summer may be found grazing in early morning on the level spaces frequently found in the river valleys at elevations of about 15,000 feet. It is excessively shy and difficult to approach. The large size of the narial aperture in the skull of Chiru is suggestive of a connection with respiration at a high altitude, but this appears to be negatived by the occurrence of the same feature in the Saiga.

_Gazella._[226]—Delicately built and sandy-coloured Antelopes, with lyrate or recurved horns, which may be absent in the female, and are always smaller and simpler in that sex than in the male. Skull with moderate lachrymal fossa, and a distinct lachrymal fissure. Vertebræ: C 7, D 13, L 6, S 4, C 14. Suborbital gland frequently small, and covered with hair. Face with a white streak running from the outer side of the base of each horn nearly down to the upper end of each nostril, cutting off a dark triangular central patch, and bordered externally by a diffused dark line (see Fig. 121, p. 310). The Gazelles, of which there are some twenty-four existing species, are typically Palæarctic desert forms, the Springbok (_G. euchore_) being an outlying South African species. _G. picticaudata_ and _G. gutturosa_ are respectively found in Western Tibet and Mongolia, the former at great elevations. The majority of the Gazelles do not exceed 30 inches in height, although _G. mohr_ is 36. Sir Victor Brooke classifies[227] the Gazelles as follows:—

A. No stripe on back; three lower premolars.

_a._ White of rump not encroaching on the fawn of the haunches.

I. Female with horns.

1. Horns lyrate or sublyrate—_G. dorcas_, _G. isabella_, _G. rufifrons_, _G. lævipes_, _G. tilonura_, _G. naso_.

2. Horns non-lyrate—_G. cuvieri_, _G. leptoceros_, _G. spekei_, _G. arabica_, _G. bennetti_, _G. fuscifrons_, _G. muscatensis_.

II. Female without horns.

_G. subgutturosa_, _G. gutturosa_, _G. picticaudata_.

_b._ White of rump projecting forwards in an angle into the fawn colour of the haunches. Horns in both sexes.

_G. dama_, _G. mohr_, _G. soemmerringi_, _G. granti_ (Fig. 121), _G. thomsoni_.

B. A white stripe down the back, two lower premolars. Horns in both sexes.—_G. euchore._

The East African _G. walleri_ is an aberrant species, in which the females are hornless, which has been made the type of the genus _Lithocranius_. It is characterised by the extreme density of the horns and skull, the slenderness of the mandible, and the small size of the cheek-teeth, the upper molars being relatively broader and lower than usual. The cranium is remarkable for the shortness of its facial portion, the large size and production backwards of the supraoccipital, and for the circumstance that the long basicranial axis is nearly parallel with the plane of the palate.

Fossil species of _Gazella_ are found in the Pliocene and Pleistocene deposits of Europe and India. _G. deperdita_ (_brevicornis_), of the Lower Pliocene of France and Greece, appears to be a generalised species in which the lower molars frequently have accessory columns, traces of which are found in some of the existing forms.

_Hippotragine Section._—Includes very large African Antelopes, with long horns, present in both sexes, which are placed over or behind the orbit, and are either recurved, straight, or subspiral. Skull with no distinct pits at apertures of supraorbital foramina in frontals, no lachrymal fossa, and only a small lachrymal fissure. No suborbital gland. Tail long, cylindrical, and tufted at the end. Upper molars extremely hypsodont, very broad, and with large accessory columns, thus closely resembling those of the Oxen. Some authorities divide this section into two. In the Pliocene it occurs in India and Europe.

_Hippotragus._[228]—Horns stout, rising vertically from a crest over the orbit at an obtuse angle to the plane of the nasals, then recurved; lachrymal fissure in some instances almost obliterated. Neck with an erect recurved mane. Tail very distinctly tufted. Four species, tropical Africa and south to the Cape.

The Sable Antelope (_H. niger_) is one of the best-known examples of this genus, occurring in South and East Africa. It stands upwards of 4½ feet in height at the withers, and, except for some white streaks on the face and the whole of the under surface of the body, is of a black colour. The Blaubok (_H. leucophæus_) is distinguished by the glaucous hue of the hair. The other species are the Equine Antelope (_H. equinus_) and Baker’s Antelope (_H. bakeri_) from the Sudan, both closely allied, but the latter distinguished by its pale fulvous colour, pencilled ears, and black stripes on the shoulder.

Skulls of fossil Antelopes from the Pliocene of India have been referred to _Hippotragus_ (_H. sivalensis_), and Sir V. Brooke suggests that the European Pliocene _Antilope recticornis_ is not generically separable.

_Oryx._[229]—Horns long, slender, nearly straight or somewhat recurved, rising behind the orbit, and inclining backwards in the plane of the nasals; lachrymal fossa distinct. Nape maned; tail long, and more haired than in _Hippotragus_. Four species, ranging over all the African deserts to Arabia and Syria.

The Gemsbok (_O. gazella_, Fig. 141), is a South African species characterised by its straight horns, the presence of a tuft of hair on the throat, as well as by the large patches and stripes of black on the head, back, limbs, and flanks. It stands nearly 4 feet in height at the shoulder, and the horns are 2 feet 9 inches in length. The colour of the upper part of the body is a rusty gray, and of the under part white, while these are separated from each other by a well-defined black band on either side. These bands unite on the breast, and are continued as a single black band until reaching the lower jaw, where they again divide and form two transverse bands on the head, terminating at the base of the horns. The head otherwise is white, as also are the limbs, with the exception of the thighs, which are black. The Gemsbok generally goes in pairs, or in small herds of three or four. The Beisa (_O. beisa_) of Abyssinia is distinguished by the absence of the tuft of hair on the throat. Writing of this species in his _Geology and Zoology of Abyssinia_, Mr. W. T. Blanford observes that “the appearance of a herd of Oryx is very imposing. They are some of the most elegant and symmetrical of animals, the motions being those of a wild Horse rather than of an Antelope. Their favourite pace appears to be either a steady quick walk or a trot; they rarely break into a gallop unless greatly alarmed. When frightened they dash off, sometimes snorting and putting their heads down as if charging, raising their long tails, and looking very formidable. They are wary animals, though far less so than some other Antelopes. It is said that they frequently attack when wounded, and their long straight horns are most deadly weapons.” The Arabian Beatrix Antelope (_O. beatrix_) is a much smaller animal, with the black markings confined to the head, fore limbs, and flanks. Finally, the Leucoryx (_O. leucoryx_) of North Africa, while agreeing in size with the Beatrix, differs by its curved horns and uniform coloration.

[Illustration: FIG. 141.—The Gemsbok (_Oryx gazella_).]

The extinct _Palæoryx_, of the Lower Pliocene of Europe and the Isle of Samos, appears to have been an ancestral form of _Oryx_, said to show some signs of affinity with _Hippotragus._

_Addax._[230]—Horns with the same inclination as in _Oryx_, but with a slight spiral twist. No mane on nape, but a slight one on the throat. Hoofs rounded. One species (_A. nasomaculatus_), from North Africa and Arabia, the colour of which is nearly white.

_Tragelaphine Section._—Includes large, so-called Bovine, Antelopes now mainly characteristic of the Ethiopian region, but with one Oriental genus. Horns usually present in the male only (if developed in the female smaller), with a more or less distinct ridge in front, and usually twisted spirally, the front ridge twisting outwards from the base of the horn. Skull without lachrymal fossa, but with a large or small lachrymal fissure; usually large pits at the apertures of the supraorbital foramina on the frontals; premaxillæ reaching nasals. Muffle large and moist; nostrils approximated. Molars hypsodont or brachydont. Vertical white stripes frequently present on the body.

_a._ _Hind limbs much shorter than the fore. Horns behind the orbit, short, conical, faintly angulated. Nose bovine. Body without vertical stripes. Molars_ (Fig. 123, p. 311) _hypsodont, with a large accessory column in those of the upper jaw. One Oriental genus._

_Boselaphus._[231]—The one genus of this subsection is represented only by the well-known Nilghai (_B. tragocamelus_) of India. The male stands over 4 feet in height at the shoulder, with horns about 8 inches in length; the hornless female being about one third smaller. Both sexes have a short erect mane, and the male has also a tuft of hair upon the throat. When adult the sexes are very different in colour, the male being of a dark iron gray or slate colour, approaching black on the head and legs, while the female and young are of a bright light brown or fawn colour. In both male and female at all ages the lips, chin, and under parts, as well as two transverse stripes on the inner sides of the ears and rings on the fetlocks, are white, and the mane and tip of the tail black. The Nilghai is one of the few Antelopes occurring in India, where it is found from near the foot of the Himalaya to the south of Mysore, though rare to the north of the Ganges and also in the extreme south. It is most abundant in Central India, and does not occur in Assam or the countries to the east of the Bay of Bengal. It frequents forests and low jungles, though often found in tolerably open plains, associating in small herds. One, or very often two, young produced at a birth. Fossil remains of species of this genus occur in the Pleistocene and Pliocene deposits of India.

_b._ _Fore and hind limbs equal. Horns long, and spirally twisted. Nose cervine, and aperture of suborbital gland very small. Body generally striped. Molars brachydont, those of the upper jaw in existing forms with a smaller inner accessory column. Three existing Ethiopian genera._

_Tragelaphus._[232]—Female hornless. Horns of males (Fig. 142) over orbit, with one or two spiral turns, obscurely ridged, the posterior ridge being more developed than the anterior. Skull with small supraorbital pits, very small lachrymal fissure, and no deep intercornual depression in the frontals. Neck maned or smooth. Hoofs short or long. Coloration usually brilliant, differing markedly in the two sexes, and the white bands on the body, when present, numerous and distinct. Seven species.

[Illustration: FIG. 142.—Head of _Tragelaphus gratus_. From Sclater, _Proc. Zool. Soc._ 1883, p. 36.]

The Harnessed Antelopes are among the handsomest of the whole group. The small Guib (_T. scriptus_) is not larger than a Goat, but _T. angasi_ is 3 feet 4 inches in height at the shoulder. In _T. scriptus_, _T. angasi_, and _T. euryceros_, the two sexes differ in colour, the body is marked by white stripes descending from a white dorsal streak, and the hoofs are short; the third species differing from the others by the absence of a mane on the neck, back, and belly. _T. gratus_ agrees with this group in coloration (the mane being absent), but differs in the extreme elongation of its hoofs. The Nakong, _T. spekei_, while having the long hoofs of _T. gratus_, has a perfectly plain body coloration, with a mane on the neck. The two species with elongated hoofs inhabit swampy districts, for which this peculiar structure is admirably adapted; and the Nakong, when frightened, will rush into the water and leave only its nostrils and the tips of the horns above the surface. The small Bushbuck (_T. sylvaticus_) of South Africa has no stripes, and short hoofs.

[Illustration: FIG. 143. The Kudu (_Strepsiceros kudu_). From Sclater, _List of Animals in Zoological Society’s Gardens_, 1883, p. 136.]

_Strepsiceros._[233]—Females hornless. Horns (Fig. 143) more twisted than in _Tragelaphus_, forming an open spiral, with the anterior ridge very strongly developed, and rising at an obtuse angle to the plane of the nasals. Skull with large supraorbital pits, large lachrymal fissure, and deep intercornual depression. Hoofs short. Body with white vertical stripes descending from a longitudinal dorsal streak. Two existing species.

The Kudu (_S. kudu_, Fig. 143) extends from South Africa to Abyssinia, and is only inferior in size to the Eland. The horns are about 4 feet in length, and form a very open spiral, and there is a fringe of long hair down the front of the neck. The Lesser Kudu (_S. imberbis_), of Somali-land is a much smaller form, without the fringe of hair on the neck, and with a much smaller axis formed by the spiral of the horns.

An imperfect skull from the Pliocene of Northern India has been referred to _Strepsiceros_.

_Oreas._[234]—Females horned. Horns twisted on their own axis, with very strong ridges, inclining upwards and outwards in the plane of the nasals. General characters of skull as in preceding genus. Stripes on body, if present, very faintly marked. One existing species.

The Eland (_O. canna_) is the largest of all the Antelopes, the males standing nearly 6 feet at the withers. One variety from South Africa is of a uniform pale fawn colour, while the Central African form is of a bright tan colour, marked by a number of thin pale vertical stripes descending from a dark dorsal ridge—these markings fading more or less in the adults. The males have a large dewlap, a tuft of brown hair on the forehead, and a small mane on the neck. The straight black horns of the male are usually about 18 inches long. Elands were formerly extremely abundant in Southern and Eastern Africa, but their destruction has been so relentless that they have totally disappeared from extensive areas, and are daily becoming scarcer.

Portions of upper jaws from the Pliocene deposits of India appear to indicate the former existence in that area of large Antelopes closely allied to the Eland, but distinguished from the living species by the greater size of the inner accessory column in the upper molars.

_Allied Extinct Types._—Large Antelopes with spirally twisted horns appear to have been common over Southern Europe in Pliocene times, but their exact affinity is in many cases difficult to determine. Of these, _Palæoreas_, which occurs in the Lower Pliocene of Europe and Algeria, appears to present affinities both to _Oreas_ and _Strepsiceros_, and may have been the ancestral type from which these two genera are derived; the upper molars have well-developed accessory columns.

The so-called _Antilope torticornis_, of the French Pliocene, resembles _Tragelaphus_ in the greater development of the posterior as compared with the anterior ridge of the horn-cores, and has accordingly been referred to that genus. _Protragelaphus_, of the Lower Pliocene of Attica, differs from all the other types in the absence of the anterior ridge on the horn-cores and of the supraorbital pits, while it has a distinct lachrymal fossa.

In this place it will be convenient to notice certain fossil forms which do not accord with any of the existing sections of the family, and for the reception of which the _Palæotragine_ section has been formed. In these types the horn-cores are laterally compressed like those of the modern Goats, but the upper molars resemble those of the brachydont Antelopes. The earliest of these genera, and the first representative of the Antelopes yet known, is _Protragoceros_, of the Middle Miocene of France, first described as _Antilope clavata_; _Palæotragoceros_ and _Tragoceros_, of the Lower Pliocene, are distinguished by their larger horns and wider molars.

A remarkable large Antelope from the Lower Pliocene of the Isle of Samos, in the Turkish Archipelago, proposed to be described as _Criotherium_, appears to be unlike any other form. The horns, which are placed on the extreme vertex of the skull, are very short, tightly twisted, and project in front of the forehead. The upper molars have short and broad crowns, with no accessory column on the inner side.

_Rupicaprine Section._—The Caprine Antelopes, as the typical members of this section may be termed, appear to connect the true Antelopes with the Goats. They are mostly small or medium-sized forms, inhabiting portions of the Palæarctic and Oriental regions, with one outlying North American genus. The typical forms present the following features. Horns present, and of nearly equal size in both sexes, rising behind the orbits, short, ringed at the base, conical or somewhat compressed, and recurved. Suborbital gland generally present, in some cases small. Build clumsy; hoofs large; tail short, tapering, hairy above. Skull with lachrymal fossa, but no fissure. Molars as in the Caprine section.

_Rupicapra._[235]—Horns short and cylindrical, rising perpendicularly from the forehead for some distance, then bending sharply backwards and downwards, forming hooks with pointed tips. Premaxillæ not reaching the nasals. One species, Palæarctic.

The Gemse, or Alpine Chamois (_R. tragus_), inhabits the high mountains of Europe from the Pyrenees to the Caucasus. It stands about 2 feet in height at the withers. The body is covered in winter with long hair of a chestnut-brown colour, that of the head being paler, with a dark brown streak on each side. At other seasons the colour is somewhat lighter, in spring approaching to gray. Underneath the external covering the body is further protected from cold by a coat of short thick wool of a grayish colour. The tail is black; the ears are pointed and erect; the hoofs have the outer edges higher than the soles, and are thus admirably adapted for laying hold of the slightest projection or roughness on the face of the rocky precipices it frequents. The Chamois is gregarious, living in herds of fifteen or twenty, and feeding generally in the morning or evening. The old males, however, live alone, except in the rutting season, which occurs in October, when they join the herds, driving off the young males, and engaging in contests with each other that often end fatally. The period of gestation is twenty weeks, when the female, beneath the shelter of a projecting rock, produces one and sometimes two young. In summer the Chamois ascends to the limits of perpetual snow, being only outstripped in the loftiness of its haunts by the Ibex; and during that season it shows its intolerance of heat by choosing such browsing grounds as have a northern exposure.

[Illustration: FIG. 144.—_Nemorhædus crispus._ From Sclater, _List of Animals in Zoological Society’s Gardens_, 1883, p. 151.]

_Nemorhædus._[236]—Horns rounded, gradually recurving, without distinct hook at the end. Suborbital gland small or wanting; ears large; skull with a large lachrymal depression, and the premaxillæ not quite reaching the nasals. Some nine species, ranging from the Eastern Himalayas to North China and Japan, and southwards to Formosa, the Malay Peninsula, and Sumatra. The smallest species is the Himalayan Goral (_N. goral_). Of the larger forms we may mention the Himalayan Serow (_N. bubalinus_) the Cambing-Utan (_N. sumatrensis_) of Sumatra, and the Japanese _N. crispus_ (Fig. 144). Of the Serow, Colonel Kinloch remarks that “it is a large and powerful beast. The body is covered with very coarse hair, which assumes the form of a bristly mane on the head and shoulders, and gives the beast a ferocious appearance, which does not belie its disposition. The colour is a dull black on the back, bright red on the sides, and white underneath, the legs also being dirty white. The ears are very large, the muzzle is coarse. The Serow has an awkward gait, but in spite of this can go over the worst ground; and it has perhaps no superior in going down steep hills. It is a solitary animal, and nowhere numerous.”

_Haploceros._[237]—The Rocky-Mountain Goat (_Haploceros montanus_), inhabiting the northern parts of California, appears to be very closely allied to _Nemorhædus_. The horns are somewhat compressed at the base; there is no suborbital gland; and the ears are small. The hair, which is whitish in colour, is very long, and especially abundant in the region of the throat, shoulders, flanks, and tail. The animal is about the size of a large Sheep.

_Budorcas._[238]—The Takin (_B. taxicolor_) of the Mishmi Hills in Assam, and an allied species from Eastern Tibet, are larger forms apparently related to _Nemorhædus_, but with a much greater development of the horns. The horns of what is considered to be the male[239] arise from the vertex of the skull, and are nearly in contact in the middle line; they first bend outwards and downwards, and then suddenly upwards and backwards. Those regarded by Mr. Hume as referable to the female are directed at first outwards, and then gradually curve upwards and backwards, without any downward flexure or angulation. The horns of the male may be 2 feet in length, with a basal diameter of 13 inches. The muzzle is hairy, with a small naked muffle. There appear to be considerable seasonal and sexual variations in colour; the body being in some cases of a yellow dun, while in others it is a dusky, reddish-brown, with much black intermingled. The heads of large males are blackish.

Scarcely anything is known of the habits of the Takin, which never appears to have been seen alive by Europeans.

_Caprine Section._—Both sexes with horns, but those of the female small. Horns usually compressed, triangular, with transverse ridges, and either curving backwards or spiral. Muzzle hairy, without naked muffle. Suborbital gland small or absent; lachrymal fossa of skull present or absent. Tail short and flattened. Foot-glands frequently present. Molars very hypsodont; those of the upper jaw being narrow, without an accessory internal column. Mainly Palæarctic, but with some outlying forms.

This section includes the Goats and Sheep, which are so closely connected that it is difficult to give well-marked generic characters that will hold good for all the species. They seem to be one of the latest developments of the _Bovidæ_, since they are unknown before the Pliocene period; and are essentially mountain forms.

[Illustration: FIG. 145.—The Alpine Ibex (_Capra ibex_).]

_Capra._[240]—Horns flattened from side to side, and either curving backwards (Fig. 145) or spirally twisted. No suborbital gland, and no lachrymal fossa in the skull. Foot-glands, if present, only in the fore feet. Chin more or less bearded. Males with a strong odour. Vertebræ: C 7, D 13, L 6, S 4, C 9-13. Some dozen species, ranging over all the higher mountains of Southern Europe, from Spain to the Caucasus; also found in Abyssinia, Persia, Sind, and Baluchistan, thence through the higher Himalaya, and so on to Tibet and Northern China. One outlying species occurs in the Nilgherries of Southern India.

The European Ibex or Steinbok (Fig. 145), which may be taken as a typical Goat, stands about 2½ feet in height at the shoulder. In summer the hair is short and smooth, and of an ashy-gray colour, but a long coat is developed in winter. The horns of the male rise in a bold backward sweep from the forehead, and are characterised by the strong transverse ridges on the broad and flat anterior surface. They are said to be not more than some 2 feet in length, but these dimensions are greatly exceeded by the horns of the Himalayan Ibex. The Alpine Ibex lives at a greater height than the Chamois, spending the day just at the limit of perpetual snow, and descending at night to graze at lower levels. Both this and the Himalayan species generally live in small herds of from five to fifteen or more; they are wary animals, although not so much so as many of the wild Sheep. The following list, mainly taken from two papers by Mr. Sclater,[241] gives the distribution of the various species of Goats, with some remarks on their peculiarities:—

(1) _C. ibex_, confined to the Alps of Switzerland, Savoy, and the Tyrol, and now nearly extinct, except where artificially preserved. (2) _C. sibirica_, closely allied to the preceding, but with larger horns, occurs in the Altai Mountains, and throughout the Himalaya from Kashmir to Nipal, and northward towards Turkestan. (3) _C. sinaitica_, of the mountains of Upper Egypt, the Sinaitic Peninsula, and Palestine, is allied to the two preceding species, but has the horns somewhat more compressed, with a difference in the ridges on the front. (4) _C. caucasica_, a very distinct species, confined to the Caucasus, where it inhabits the western part of the Great Caucasus; with thick horns curving backwards and outwards in one plane, with the exception of their tips, which incline inwards.[242] (5) _C. pallasi_ is an allied species from the Eastern Caucasus, distinguished, among other features, by the curvature of the horns, which lie flatter and twist more outward from the forehead, with a greater terminal inward bend. (6) _C. pyrenaica_, of the Pyrenees, and the higher ranges of Central Spain, Andalusia, and Portugal, is another nearly related species. (7) _C. ægagrus_, formerly abundant over the Grecian Archipelago, but now restricted in Europe to Crete and some of the Cyclades, is found throughout the mountains of Asia Minor and Persia, and thence to Baluchistan and Sind. The horns are thinner and sharper in front than in the Ibexes, and this species is generally regarded as the ancestral stock of the various breeds of domestic Goats. (8) _C. dorcas_, a Goat from the island of Jura, near Eubœa, has been described under this name, and is apparently nearly allied to _C. ægagrus_. (9) _C. walie_, an apparently well-characterised species from the highest ranges of Abyssinia. (10) _C. falconeri_; the Markhoor differs from all the preceding species by the spiral twisting of its horns, which attain enormous dimensions. It occurs in the Pir-Panjal range south of Kashmir, and thence into Afghanistan and the Suleiman range, and northwards to Astor, Gilgit, and Scardo (Baltistan). The specimens from the Suleiman range have the spiral of the horns very close, somewhat as in the Eland; while in those from Astor, Gilgit, and Scardo it is very open, as in the Kudu. The Pir-Panjal race occupies a somewhat intermediate position in this respect. (11) _C. jemlaica_, the Thar, inhabits suitable regions along the whole range of the Himalaya from Kashmir to Bhutan. Together with the next species, it differs from the more typical Goats in its short, thick, and much compressed horns, the anterior border of which is keeled, and the moist naked muffle. There are no glands in the fore feet. It was generically separated by Gray as _Hemitragus_. (12) _C. hylocrius_, the so-called Ibex of the Nilgherries, Anamallays, and other adjoining ranges of Southern India, is an outlying species, apparently allied to the preceding, but with somewhat different horns, in which the external angle in front is much rounded off.

Of fossil Goats we have but little knowledge. Remains of _C. pyrenaica_ are found in cave-deposits at Gibraltar; and it is not improbable that the genus is represented in the Upper Pliocene of France. Several species occur in the Pliocene of India, _C. sivalensis_ being apparently closely allied to _C. jemlaica_, while another has horns resembling those of _C. falconeri_, and it is possible that a third may be more nearly related to the Ibexes.

_Ovis._[243]—Horns curving backwards and downwards in a bold sweep, with the tips everted, generally with more or less prominent transverse ridges, and brownish in colour. Suborbital gland and lachrymal fossa usually present, but generally small. Foot-glands in all the feet. Chin not bearded;[244] males without a strong odour. Vertebræ: C 7, D 13, L 6, S 4, C 10-14. Some twelve species, mainly Palæarctic, but extending into the adjacent portions of the Oriental region, and with one outlying species in North America.

The more typical Sheep are closely connected with the Goats by the Himalayan Bharal (_O. nahura_) and the Aoudad (_O. tragelaphus_) of Northern Africa, both these species having no suborbital gland and no lachrymal fossa, while their comparatively smooth and olive-coloured horns show a decided approximation to those of the Goats. Both present, however, the ovine character of glands in all the feet. In the typical Sheep the basioccipital of the skull is wider in front than behind, with the anterior pair of tubercles widely separated and much larger than the posterior pair. The Bharal, however, resembles the Goats in having an oblong basioccipital, with the posterior tubercles larger and more prominent than the anterior ones, both being situated in the same antero-posterior line. These transitions towards the caprine type are, however, not sufficient to support the view that the Bharal should form the type of a distinct genus (_Pseudois_), more especially since some of the typical Sheep, like _O. canadensis_, have the lachrymal fossa of the skull very much reduced in size.

The distinction of the various permanent modifications under which wild Sheep occur is a matter of considerable difficulty. Trivial characters, such as size, slight variations in colour, and especially the form and curvature of the horns, are relied upon by different zoologists who have given attention to the subject in the discrimination of species, but no complete accord has yet been established. The most generally recognised forms are enumerated below.

The geographical distribution of wild Sheep is interesting. The immense mountain ranges of Central Asia, the Pamir and Thian-Shan of Turkestan, may be looked upon as the centre of their habitat. Here, at an elevation of 16,000 feet above the sea-level, is the home of the magnificent _Ovis poli_, named after the celebrated Venetian traveller Marco Polo, who met with it in his adventurous travels through this region in the thirteenth century. It is remarkable for the great size of the horns of the old rams and the wide open sweep of their curve, so that the points stand boldly out on each side, far away from the animal’s head, instead of curling round nearly in the same plane, as in most of the other species. A Sheep from the same region, in which the horns retain their more normal development, has received the name of _O. karelini_, but, according to Mr. W. T. Blanford,[245] is not distinct specifically from _O. poli_. Eastward and northward is found the Argali (_O. argali_), with a wide and not very well determined range; it formerly occurred in the Altai, but is now found in Northern Mongolia. Still farther north, in the Stanovoi Mountains and Kamschatka, is _O. nivicola_, and away on the other side of Behring’s Strait, in the Rocky Mountains and adjacent highlands of western North America, is the “Bighorn” or Mountain Sheep (_O. canadensis_), the only member of the genus found in that continent, and indeed—except the Bison, Musk-Ox, Mountain Goat (_Haploceros_), and the Prong-buck (_Antilocapra_)—the only hollow-horned Ruminant, being like the rest obviously a straggler from the cradle of its race. The two last-named species are nearly allied, and are characterised by the slight development of the ridges on their horns and the very shallow lachrymal fossa. Turning southward from the point from which we started, and still a little to the east, in Nipal and Western Tibet, is the Himalayan Argali (_O. hodgsoni_), having massive and strongly curved horns, with bold ridges, like those of the true Argali. Indeed, were it not for their isolated areas there would appear to be no grounds for distinguishing these two closely allied forms, and it is not improbable that they are really identical. _O. brookei_, appears to have been founded on a hybrid between _O. hodgsoni_ and _O. vignei_. In the same districts, and also in Southern Ladak, there occurs the Bharal (_O. nahura_), with smaller, smoother, and more spreading horns. Passing in a south-westerly direction we find a series of smaller forms, _O. vignei_ of Ladak, _O. cycloceros_ of Northern India, Persia, and Baluchistan. _O. gmelini_ of Asia Minor and Persia, _O. ophion_, confined to the elevated pine-clad Troodos Mountains of the island of Cyprus, and said at the time of the British occupation in 1878 to have been reduced to a flock of about twenty-five individuals, and _O. musimon_, the Moufflon of Corsica and Sardinia (see Fig. 146), believed to have been formerly also a native of Spain. In the three latter species the females are hornless. Lastly, we have the somewhat aberrant, Goat-like Aoudad (_O. tragelaphus_), of the great mountain ranges of North Africa, in which, as already mentioned, the skull and horns resemble those of the Bharal, although the tail is longer, and there is a thick fringe of long hair on the throat, chest, and fore legs.

[Illustration: FIG. 146.—The Moufflon (_Ovis musimon_). From a living animal in the London Zoological Gardens.]

We thus find that Sheep are essentially inhabitants of high mountainous parts of the world, for dwelling among which their wonderful powers of climbing and leaping give them special advantages. No species frequent by choice either level deserts, open plains, dense forests, or swamps. By far the greater number of species are inhabitants of the continent of Asia, one extending into North America, one into Southern Europe, and one into North Africa. No wild Sheep exist in any other part of the world, unless the so-called Musk-Ox of the Arctic regions, the nearest existing ally to the true Sheep, may be considered as one. Geologically speaking, Sheep appear to be very modern animals, or perhaps it would be safer to say that no remains that can be with certainty referred to the genus have been met with in the hitherto explored true Tertiary beds, which have yielded such abundant modifications of Antelopes and Deer. They are generally considered not to be indigenous in the British Isles, but to have been introduced by man from the East in prehistoric times. A fossil Sheep (_Ovis savigni_), apparently allied to the Argali, has, however, been described from the so-called Forest-bed of the Norfolk coast.

The Sheep was a domestic animal in Asia and Europe before the dawn of history, though quite unknown as such in the New World until after the Spanish conquest. It has now been introduced by man into almost all parts of the world where settled agricultural operations are carried on, but flourishes especially in the temperate regions of both hemispheres. Whether our well-known and useful animal is derived from any one of the existing wild species, or from the crossing of several, or from some now extinct species, is quite a matter of conjecture. The variations of external characters seen in the different domestic breeds are very great. They are chiefly manifested in the form and number of the horns, which may be increased from the normal two to four or even eight, or may be altogether absent in the female alone, or in both sexes; in the form and length of the ears, which often hang pendent by the side of the head; in the peculiar elevation or arching of the nasal bones in some Eastern races; in the length of the tail, and the development of great masses of fat at each side of its root, or in the tail itself; and in the colour and quality of the fleece.

_Ovibos._[246]—This genus is generally considered to be a connecting link between the Caprine and Bovine sections, but should rather be regarded as an aberrant type of the former. Horns of adult male rounded, smooth, and closely approximated at their bases, where they are depressed and rugose; curving downwards, and then upwards and forwards. Muzzle caprine; no suborbital gland, no lachrymal fossa or fissure in skull; orbits tubular; a large narial aperture and very short nasals; premaxillæ not reaching nasals. Tail short, and molar teeth caprine. One existing and two fossil species, Palæarctic and Nearctic.

[Illustration: FIG. 147.—The Musk-Ox (_Ovibos moschatus_).]

The animal commonly known as the Musk-Ox (_Ovibos moschatus_), though approaching in size the smaller varieties of Oxen, is in structure and habits closely allied to the Sheep, its affinities being well expressed by the generic name _Ovibos_ bestowed upon it by De Blainville. The specific name, as also the common English appellatives “Musk-Ox,” “Musk-Buffalo,” or “Musk-Sheep,” applied to it by various authors, refer to the musky odour which the animal exhales. This does not appear to be due to the secretion of a special gland, as in the case of the Musk-Deer; but it must be observed that, except as regards the osteology, very little is known of the anatomy of this species. It about equals in size the small Welsh and Scotch cattle. The head is large and broad. The horns in the old males have extremely broad bases, meeting in the median line, and covering the brow and whole crown of the head. They are directed at first downwards by the side of the face and then turn upwards and forwards, ending in the same plane as the eye. Their basal halves are of a dull white colour, oval in section and coarsely fibrous; their middle part smooth, shining, and round; their tips black. In the females and young males the horns are smaller, and their bases are separated from each other by a space in the middle of the forehead. The ears are small, erect, and pointed, and nearly concealed in the hair. The space between the nostrils and the upper lip is covered with short close hair, as in Sheep and Goats, without any trace of the bare muffle of the Oxen. The greater part of the animal is covered with long brown hair, thick, matted, and curly on the shoulders, so as to give the appearance of a hump, but elsewhere straight and hanging down,—that of the sides, back, and haunches reaching as far as the middle of the legs and entirely concealing the very short tail. There is also a thick woolly under-fur, shed in the summer. The hair on the lower jaw, throat, and chest is long and straight, and hangs down like a beard or dewlap, though there is no loose fold of skin in this situation as in Oxen. The limbs are stout and short, terminating in unsymmetrical hoofs, the external one being rounded, the internal pointed, and the sole partially covered with hair.

The Musk-Ox is at the present day confined to the most northern parts of North America, where it ranges over the rocky barren grounds between the 60th parallel and the shores of the Arctic Sea. Its southern range is gradually contracting, and it appears that it is no longer met with west of the Mackenzie River, though formerly abundant as far as Eschscholtz Bay. Northwards and eastwards it extends through the Parry Islands and Grinnell Land to North Greenland, reaching on the west coast as far south as Melville Bay; and it was also met with in abundance by the German polar expedition of 1869-70 at Sabine Island on the east coast. No trace of it has been found in Spitzbergen or Franz Joseph Land. As proved by the discovery of fossil remains, it ranged during the Pleistocene period over northern Siberia and the plains of Germany and France, its bones occurring very generally in river deposits along with those of the Reindeer, Mammoth, and Woolly Rhinoceros. It has also been found in Pleistocene gravels in several parts of England, as Maidenhead, Bromley, Freshfield near Bath, Barnwood near Gloucester, and also in the lower brick-earth of the Thames valley at Crayford, Kent.

It is gregarious in habit, assembling in herds of twenty or thirty head, or, according to Hearne, sometimes eighty or a hundred, in which there are seldom more than two or three full-grown males. The Musk-Ox runs with considerable speed, notwithstanding the shortness of its legs. Major H. W. Feilden, naturalist to the Arctic expedition of 1875, says: “No person watching this animal in a state of nature could fail to see how essentially ovine are its actions. When alarmed they gather together like a flock of sheep herded by collie dog, and the way in which they pack closely together and follow blindly the vacillating leadership of the old ram is unquestionably sheep-like. When thoroughly frightened they take to the hills, ascending precipitous slopes and scaling rocks with great agility.” They feed chiefly on grass, but also on moss, lichens, and tender shoots of the willow and pine. The female brings forth a single young one in the end of May or beginning of June after a gestation of nine months. According to Sir J. Richardson, “when this animal is fat its flesh is well tasted, and resembles that of the Caribou, but has a coarser grain. The flesh of the bulls is highly flavoured, and both bulls and cows when lean smell strongly of musk, their flesh at the same time being very dark and tough, and certainly far inferior to that of any other ruminating animal existing in North America.” The carcase of a Musk-Ox weighs, exclusive of fat, above 3 cwt. On this subject, Major Feilden[247] says: “The cause of the disagreeable odour which frequently taints the flesh of these animals has received no elucidation from my observations. It does not appear to be confined to either sex, or to any particular season of the year; for a young unweaned animal, killed at its mother’s side and transferred within an hour to the stew-pans, was as rank and objectionable as any. The flesh of some of these animals of which I have partaken was dark, tender, and as well flavoured as that of four-year old Southdown mutton.”

Remains of two fossil species of this genus (_O. bombifrons_ and _O. cavifrons_) have been described from Pleistocene beds in the United States, the one from Kentucky and the other from the Arkansas River. Both (if indeed they be valid species) appear closely allied to the living form.

_Bovine Section._—Horns present and of nearly equal size in both sexes; in form rounded or angulated, placed on or near the vertex of the skull, extending more or less outwards, and curving upwards near the extremities; external surface comparatively smooth and never marked by prominent transverse ridges or knobs. Muzzle broad, with large naked muffle; nostrils lateral; no suborbital gland. Skull without any trace of lachrymal fossa or fissure. Tail long and cylindrical; generally tufted at the extremity, rarely hairy throughout. Males usually with a dewlap on the throat. No foot-glands. Molar teeth extremely hypsodont; those of the upper jaw with a nearly square cross-section, and a large accessory inner column.

The section is abundantly represented in the Palæarctic, Oriental, and Ethiopian regions, with one Nearctic species and an outlying and aberrant species in Celebes.

_Bos._[248]—The whole of the species of Oxen were included by Linnæus in the single genus _Bos_, and although the species have been distributed by modern zoologists in several genera—such as _Anoa_, _Bubalus_, _Bison_, _Poëphagus_, _Bibos_, and _Bos_—the characters by which they are separated are so slight that it seems, on the whole, preferable to retain the old genus in its original wide sense. Using then the term _Bos_ in this sense, it will include all the representatives of the section—about a dozen in number—and may be divided into several groups.

The first group includes the Buffaloes (genus _Bubalus_), chiefly characterised by their more or less flattened and angulated horns, which incline upwards and backwards, with an inward curve towards their tips, and are placed below the plane of the occiput, or vertex of the skull. The premaxillæ reach to the nasals, and the vomer is peculiar in being so much ossified as to join the posterior border of the palate. The back has a distinct ridge in the region of the withers; and the forehead is frequently convex. Oriental and Ethiopian region, and Celebes.

The most generalised representative of this group is the small Anoa (_B. depressicornis_) of Celebes, the type of the genus _Anoa_ or _Probubalus_, which has the same cranial structure as in the more typical Buffaloes, to the young of which (as was pointed out by the late Professor Garrod) it presents a striking resemblance. Its colour is black; and the short and prismatic horns are directed upwards from the forehead. In the Pliocene Siwaliks of India there occur the remains of larger Buffaloes (_B. occipitalis_ and _B. acuticornis_) closely allied to the Anoa, but with longer and more distinctly angulated horns. The still larger _B. platyceros_ of the last-named deposits, in which the horns are wide-spreading and much flattened, appears to be in some respects intermediate between the preceding and following forms. The typical Indian Buffalo (_Bos buffelus_), which has been domesticated over South-East Asia, Egypt, and Southern Europe, is, in the wild state, a gigantic animal with enormous horns. These horns are longer, more slender, and more outwardly directed in the female than in the male; and in the former sex may have a length of more than 6 feet from base to tip. They are widely separated at their bases, the forehead is very convex, and the ears are not excessively large, and have no distinct fringe. These Buffaloes frequent swampy and moist districts in several parts of India, but it is in many instances difficult to decide whether they belong to really wild or to feral races. Very large skulls, specifically indistinguishable from those of the existing form, occur in the Pleistocene deposits of the Narbada valley in India; while an allied, if not specifically identical form, occurs in the Pliocene of the same country. There is some doubt whether _B. antiquus_ of the Pleistocene of Algeria is most nearly related to the Indian or to the African species.

In Africa two species of Buffalo are recognised by Sir Victor Brooke,[249] namely the large _B. caffer_, occurring typically at the Cape, but said by this writer to range to Abyssinia, and the smaller _B. pumilus_, which seems to have a very wide distribution. The skulls of both these forms are shorter than in the Indian species, while the horns are also shorter, much more curved inwardly, and more approximated on the forehead. In the large typical form of _B. caffer_ from South Africa the colour is black, the horns of the male are very thick, much reflected, and closely approximated on the forehead, where they form a helmet-like mass.[250] The large northern form described as _B. æquinoctialis_ has the horns somewhat less thick, and thus approximates to the so-called _B. pumilus_.

The latter occurs typically in Western Africa, where it has also been described as _B. brachyceros_. In the typical form the horns are thinner and less reflected than in _B. caffer_, and in some specimens they are more widely separated on the forehead, and are marked at their bases by distinct rugæ. The colour is ruddy brown, inclining to rufous in one specimen. The skulls of Buffaloes from West Africa, probably referable to the form described as _B. centralis_, appear to connect _B. pumilus_ with _B. caffer_, as shown by their larger size and the form of their horns; so that further observations are required to show whether the smaller form is really entitled to rank as a distinct species, or merely as a well-marked local race.

The second group comprises the Bisons, which are more nearly allied to the true Oxen, having similar rounded horns, but the skull being less massive, with a longer and more tapering frontal region, and a wider frontal diameter. The superior part of the forehead is transversely arched, the intercornual space elevated in the middle, the horns situated below the plane of the occiput, and the orbits more or less prominent. The premaxillæ do not extend upwards to reach the nasals. The Bisons (Fig. 148) have the body covered with short, crisp, woolly hair, while on the head and neck there is an abundance of much longer and darker hair, which forms a mane concealing the eyes, ears, and the bases of the horns. There is also a long beard beneath the chin; while a line of long hair extends from the head nearly to the tail, the latter being tufted at the extremity. The withers are much higher than the hind quarters, so that there is a kind of hump at the shoulders.

The group is represented by two species—the European and the American Bison. The former is the _Bos bonasus_ of Linnæus, and is also identical with the _Bos bison_ of Ray. The German name _Wisent_ is the equivalent of the Greek _Bison_. The American species is the _Bos americanus_ of Gmelin. Both species are closely allied, but the American Bison is slightly the smaller animal of the two, and is shorter and weaker in the hind quarters, with a smaller pelvis; its body is, however, more massive in front; and the hair on the head, neck, and fore quarters is longer and more luxuriant. A large bull American Bison, preserved in the Museum at Washington, stands 5 feet 8 inches in height at the withers. The European Bison appears to have been formerly abundant over a large portion of Europe in the Pleistocene period—the fossil race described as _B. priscus_ not being specifically distinct; but at the present day it exists only in the primeval forests of Lithuania, Moldavia, Wallachia, and the Caucasus, where it is artificially preserved.

[Illustration: FIG. 148.—The American Bison (_Bos americanus_). After Hornaday.]

The American Bison formerly ranged over about one-third of the North American continent. Thus, to quote from Mr. Hornaday,[251] “starting almost at tide-water on the Atlantic coast, it extended across the Alleghany mountain system to the prairies along the Mississippi, and southward to the delta of that great system. Although the great plain country of the West was the natural home of the species, where it flourished most abundantly, it also wandered south across Texas to the burning plains of North-Eastern Mexico, westward across the Rocky Mountains into New Mexico, Utah, and Idaho, and northward across a vast treeless waste to the bleak and inhospitable shores of the Great Slave Lake itself.” In consequence of the settlement of the country by Europeans the area inhabited by the Bison was gradually contracted, till about 1840 one mighty herd occupied the centre of its former range. The completion of the Union Pacific Railway in 1869 divided this great herd into a southern and a northern division, the former comprising a number of individuals estimated at nearly four millions, while the latter contained about a million and a half. Before 1880 the southern herd had, however, practically ceased to exist; while the same fate overtook the northern one in 1883. In 1889 some twenty stragglers in Texas represented the last of the southern herd; while there were a few others in Colorado, Wyoming, Montana, and Dakota. A herd of some two hundred wild individuals, derived from the northern herd, is preserved by the United States Government in the Yellowstone National Park; and it is believed that some five hundred of the race known as Wood-Bison exist in British territory; but with these exceptions this magnificent species is exterminated. The multitudes in which the American Bison formerly existed are almost incredible; the prairies being absolutely black with them as far as the eye could reach, and the numbers in the herds being, as we have said, reckoned by millions. Mr. Hornaday even considers that the whole of the game in South Africa was never equal to the number of Bison on an equal area of the American prairies.

[Illustration: FIG. 149.—The Yak (_Bos grunniens_), domestic variety.]

An extinct Bison from the Pleistocene of Texas, known as _Bos latifrons_, was probably the ancestor of the recent American species.

The Yak (_Bos grunniens_) appears to be allied both to the Bisons and the true Oxen, being distinguished from the former by the different position occupied by the long hair, which forms a fringe investing the shoulders, flanks, and thighs, and grows over the whole of the tail. In the skull the orbits are less tubular, the forehead flatter, and the premaxillæ less widely separated from the nasals. There is no distinct dewlap. Wild Yaks inhabit the higher regions of Chinese Tibet and the region of the Karakoram, as well as the more outlying parts of Ladak, such as the Changchemo valley. Owing, however, to incessant pursuit those now found within the territories of the Maharaja of Kashmir are stragglers from Chinese Tibet. The height of the Yak is somewhat lower than that of the larger domestic cattle. The colour of the wild race is black, tending to brown on the flanks; but many of the tame breeds which have been crossed with ordinary cattle have more or less white (Fig. 149), and it is the white tails of these half-breeds that are so esteemed in India as “chowries.” Yaks are exceedingly intolerant of heat, and the wild ones always live at very great elevations. Tame Yaks are extensively used as beasts of burden in Tibet, where they are extremely valuable in crossing the high and desolate wastes of that region; they have, however, the great drawback that they refuse to eat corn, so that in districts where there is no grass it is frequently necessary to make forced marches with wearied beasts in order to prevent them (and thus the whole party) perishing from starvation.

The skull of an extinct species from the Pliocene of Northern India, described as _Bos sivalensis_, appears to indicate a species allied to the Yak.

With the Bibovine group we come to the consideration of three Oriental species which connect the preceding forms with the typical Oxen. The three species are the Gaur (_B. gaurus_) the Gayal (_B. frontalis_, Fig. 150) of India, and the Banteng (_B. sondaicus_) of Burma, Java, Bali, and Lambok. In this group, as in the true Oxen, there are thirteen pairs of ribs, against fourteen in the Bisons. All the three species are characterised by the great height of the spines of the anterior dorsal vertebræ, causing a prominent ridge down the back. The horns, which are of a greenish colour in the Gaur, are somewhat flattened, and after running outwards are directed upwards instead of backwards; they occupy the vertex of the skull. The frontals are more or less concave, the premaxillæ do not join the nasals, and the occipital aspect of the skull is characterised by the deep incisions made by the temporal fossæ. The lower part of the legs is white (Fig. 150), and the hoofs are comparatively small and pointed. The Gaur (_B. gaurus_) is the largest of the three species, and inhabits all the large forests of India from near Cape Comorin to the foot of the Himalaya; it is commonly known to sportsmen as the Indian Bison. It stands fully 6 feet in height at the withers, which are much elevated; and since the whole back is arched the line from the nose to the root of the tail forms an almost continuous curve. The most characteristic feature of the animal is, however, the large and convex intercornual frontal crest, which curves forward, and thus gives a concave profile to this part of the skull. As a rule the Gaur prefers hilly regions, although it is sometimes met with on the flat. It is very shy and readily frightened; and it has never been domesticated. The Gayal, or Mithan, of which a figure is given in woodcut 150, is at once distinguished from the Gaur by the straight line between the horns (which are black in colour), owing to the absence of the intercornual crest of the latter. The horns are also shorter, more rounded, and less curved. In the Indian Museum, Calcutta, there are, however, skulls which are to a great extent intermediate between those of typical Gaurs and those of typical Gayals, but these may belong to hybrids. The Gayal occurs in Assam, Chittagong, and adjacent districts, but it appears that these animals exist in a semi-domesticated condition, no wild race being known to Europeans, although it is probable that such may exist in the unexplored Mishmi Hills.

[Illustration: FIG. 150.—The Gayal (_Bos frontalis_). From Sclater, _List of Animals in Zoological Society’s Gardens_, 1883.]

The Banteng (_B. sondaicus_) is a smaller and lighter built animal than either of the preceding, with a longer and sharper head, and more rounded and slender horns. The dorsal ridge is, moreover, but slightly developed; while the bright dun colour of the body of the female readily distinguishes it from the darker hue of the Gaur and Gayal.

A fossil skull from the Pleistocene deposits of the Narbada valley, India, described as _Bos palæogaurus_, is believed to indicate a species nearly allied to the Gaur, if indeed it be specifically distinct.

The true Oxen, or Taurine group, are now represented solely by _Bos taurus_ and _Bos indicus_. Both of these species are now known only by domesticated races, unless the herds of the former preserved at Chillingham and some other British parks are the survivors of an original wild race. The dorsal ridge of the Bibovine group is here wanting; the horns are rounded, with their extremities directed backwards, and are placed at the extreme vertex of the skull; while the long frontal region is nearly flat; the temporal fossæ scarcely intrude upon the occipital aspect of the skull; and the premaxillæ reach the nasals. The hoofs are large and rounded. It is known that wild Oxen were abundant in the forests of Europe at the time of Julius Cæsar, by whom they were described as the Urus, equal to the German Aurochs; and the large skulls found in turbary and Pleistocene deposits, and described under the name of _Bos primigenius_, can only be regarded as having belonged to the large original race of _B. taurus_, of which it has been thought the Chillingham cattle are smaller descendants.[252] The subfossil skulls described as _B. longifrons_ and _B. frontosus_ must also be looked upon as referable to smaller races of the same species. That the domestic cattle of Europe are descendants from the various races of the same original species there can be no doubt, but in the case of the humped cattle of India (_B. indicus_) it is quite probable that their origin may be, at least in part, different. The extinct _Bos namadicus_, of the Pleistocene deposits of India, was a species with the general characters of the Taurine group, but with an inclination to a flattening of the horns, and with an approximation to a Bibovine type of occiput, as well as with the separation of the premaxillæ from the nasals.

The earliest representatives of this group occur in the Pliocene of the Siwalik Hills in Northern India. One of these species (_B. planifrons_) appears to be allied to _B. namadicus_; but the other (_B. acutifrons_) was a gigantic species characterised by the sharp median angulation of the frontal region, and the pyriform section of the enormous horn-cores.

The extinct _B. elatus_, from the Upper Pliocene of France and Italy, is the representative of a generalised type, which may be known as the Leptobovine group. The males had rounded horn-cores widely separated at their bases, and placed low down on the forehead. The females (which have been described as _Leptobos_) were often or always hornless. The limbs were unusually slender. This group also occurs in the Pliocene of the Siwalik Hills.

_Suborder_ PERISSODACTYLA.

This is a perfectly well-defined group of Ungulate mammals, represented in the actual fauna of the world by only three distinct types or families—the Tapirs, the Rhinoceroses, and the Horses—poor in genera and species, and (except in the case of the two domesticated species of _Equus_, which have been largely multiplied and diffused by man’s agency) not generally numerous in individuals, though widely scattered over the earth’s surface. Palæontological records, however, show very clearly that these are but the surviving remnants of a very extensive and much-varied assemblage of animals, which flourished upon the earth through the Tertiary geological period, and which, if it could be reconstructed in its entirety, would not only show members filling up structurally the intervals between the existing apparently isolated forms, but would also show several marked lines of specialisation which have become extinct without leaving any direct successors.

[Illustration: FIG. 151.—Bones of right fore foot of existing Perissodactyles. A, Tapir (_Tapirus indicus_), × ⅕; B, Rhinoceros (_Rhinoceros sumatrensis_), × ⅙; C, Horse (_Equus caballus_), × ⅛. _U_, ulna; _R_, radius; _c_, cuneiform; _l_, lunar; _s_, scaphoid; _u_, unciform; _m_, magnum; _td_, trapezoid; _tm_, trapezium.—From Flower, _Osteology of Mammalia_.]

The following are the principal characters distinguishing them from the Artiodactyla. Premolar and molar teeth in continuous series, with massive, quadrate, transversely ridged or complex crowns,—the posterior premolars often resembling the true molars in size and structure. Crown of the last lower molar commonly bilobed, and if a third lobe is present in this tooth it is wanting in the last lower milk-molar. Dorso-lumbar vertebræ never fewer than twenty-two, usually twenty-three in the existing species. Nasal bones expanded posteriorly. An alisphenoid canal. Femur with a third trochanter.[253] The middle or third digit on both fore and hind feet larger than any of the others, and symmetrical in itself, the free border of the ungual phalanx being evenly rounded (see Fig. 151). This may be the only functional toe, or the second and fourth may be subequally developed on each side of it. In the Tapirs and many extinct forms, the fifth toe also remains on the fore limb, but its presence does not interfere with the symmetrical arrangement of the remainder of the foot around the median line of the third or middle digit. Traces of a hallux have only been found in some extremely ancient and primitive forms. The astragalus has a pulley-like surface above for articulation with the tibia, but its distal surface is flattened and unites to a much greater extent with the navicular than with the cuboid, which bone is of comparatively less importance than in the Artiodactyla. The calcaneum does not articulate with the lower or distal extremity of the fibula. The stomach is always simple, the cæcum is large and capacious, the placenta diffused, and the mammæ are inguinal. The gall-bladder is invariably absent.

As regards the dentition, the whole of the premolar series may be preceded by milk-teeth; and it has been demonstrated in _Rhinoceros_ that when there is no displacement of the first cheek-tooth that tooth is a persistent milk-molar; the same condition apparently holding good in _Palæotherium._ This feature indicates considerable dental specialisation, the milk-molars, according to the theory generally accepted by the leading English zoologists, being the acquired, and the premolars the original series. Another peculiar feature of the dentition of the Perissodactyla, very rarely met with among the Artiodactyla, is that the premolars tend to resemble the true molars; this feature occurring in all the existing genera, although not found in the earlier generalised types. The cheek-teeth of all the members of the suborder are primarily constructed on some modification of what is known as the lophodont plan. Thus the upper molars (Fig. 155, p. 375) have an outer antero-posterior wall from which proceed two transverse ridges, formed by the coalescence of the primitive inner and outer columns, towards the inner aspect of the crown; while in the lower molars there may be either two simple transverse ridges, or these ridges may be curved into crescents, coming into contact with one another at their extremities. Those forms having brachydont teeth show this plan of structure in its simplest modification; but in cases, as in the Horse, where the teeth assume an extremely hypsodont form, the original plan is so obscured by infoldings of the enamel that it can only be traced with difficulty.

At the present day the Perissodactyla are sharply differentiated into Horses, Tapirs, and Rhinoceroses, but the knowledge already gained of the extinct representatives of the suborder shows such a close alliance between these groups that it is exceedingly difficult to make any satisfactory classification of the whole. This is of course exactly what might have been expected; and the same would doubtless be the case with all other groups if we knew as much of their past history as we do of that of the Perissodactyles.

The detailed account of the anatomy of the Horse given in the sequel will afford much information as to the general structure of the members of the suborder.

_Family_ TAPIRIDÆ.

Both upper and lower cheek-teeth brachydont and simply bilophodont; hinder premolars as complex as the molars; last lower molar without third lobe; first upper cheek-tooth with a milk-predecessor.[254] Outer columns of upper molars conical. Four digits in the manus, and three in the pes.

_Tapirus._[255]—Dentition _i_ ³⁄₃, _c_ ¹⁄₁, _p_ ⁴⁄₃, _m_ ³⁄₃; total 42. Of the upper incisors, the first and second are nearly equal, with short, broad crowns; the third is large and conical, considerably larger than the canine, which is separated from it by an interval. Lower incisors diminishing in size from the first to the third; the canine, which is in contact with the third incisor, large and conical, working against (and behind) the canine-like third upper incisor. In both jaws there is a diastema between the canines and the commencement of the teeth of the cheek-series, which are all in contact. First upper premolar with a triangular crown, narrow in front owing to the absence of the anterior inner cusp. The other upper premolars and molars all formed on the same plan and of nearly the same size, with four roots and quadrate crowns, rather wider transversely than from before backwards, each having four cusps, connected by a pair of transverse ridges, anterior and posterior. The first lower premolar compressed in front; the others composed of a simple pair of transverse crests, with a small anterior and posterior circular ridge.

Skull elevated and compressed. Orbit and temporal fossa widely continuous, there being no true postorbital process from the frontal bone. Anterior narial apertures very large, and extending high on the face between the orbits; nasal bones short, elevated, triangular, and pointed in front. Vertebræ: C 7, D 18, L 5, S 6, C about 12. Limbs short and stout. Forefeet with four toes, having distinct hoofs: the first is absent, the third the longest, the second and fourth nearly equal, the fifth the shortest and scarcely reaching the ground in the ordinary standing position. Hind feet with the typical Perissodactyle arrangement of three toes,—the middle one being the largest, the two others nearly equal. Nose and upper lip elongated into a flexible, mobile snout or short proboscis, near the end of which the nostrils are situated. Eyes rather small. Ears of moderate size, ovate, erect. Tail very short. Skin thick and but scantily covered with hair.

The existing species of Tapir may be grouped into two sections, the distinctive characters of which are only recognisable in the skeleton. (A) With a great anterior prolongation of the ossification of the nasal septum (mesethmoid), extending in the adult far beyond the nasal bones, and supported and embraced at the base by ascending plates from the maxillæ (genus _Elasmognathus_, Gill). Two species, both from Central America, _Tapirus bairdi_ and _T. dowi_. The former is found in Mexico, Honduras, Nicaragua, Costa Rica, and Panama; the latter in Guatemala, Nicaragua, and Costa Rica. (B) With ossification of the septum not extending farther forward than the nasal bones (_Tapirus_ proper). Three species, _T. indicus_, the largest of the genus, from the Malay Peninsula (as far north as Tavoy and Mergui), Sumatra, and Borneo, distinguished by its peculiar coloration, the head, neck, fore and hind limbs, being glossy black, and the intermediate part of the body white; _T. americanus_ (_T. terrestris_, Linn.), the common Tapir of the forests and lowlands of Brazil and Paraguay (Fig. 152); and _T. roulini_, the Pinchaque Tapir of the high regions of the Andes. All the American species are of a nearly uniform dark brown or blackish colour when adult; but it is a curious circumstance that when young (and in this the Malay species conforms with the others) they are conspicuously marked with spots and longitudinal stripes of white or fawn colour on a darker ground.

The habits of all the kinds of Tapirs appear to be very similar. They are solitary, nocturnal, shy, and inoffensive, chiefly frequenting the depths of shady forests and the neighbourhood of water, to which they frequently resort for the purpose of bathing, and in which they often take refuge when pursued. They feed on various vegetable substances, as shoots of trees and bushes, buds, and leaves. They are hunted by the natives of the lands in which they live for the sake of their hides and flesh.

The singular fact of the existence of so closely allied animals as the Malayan and the American Tapirs in such distant regions of the earth, and in no intervening places, is accounted for by what is known of the geological history of the race; for the Tapirs must once have had a very wide distribution. There is no proof of their having lived in the Eocene epoch, but in deposits of Miocene and Pliocene date remains undistinguishable generically from the modern Tapirs, and described as _T. priscus_, _T. arvernensis_, etc., have been found in France, Germany, and in the Red Crag of Suffolk. Tapirs appear, however, to have become extinct in Europe before the Pleistocene period, since none of their bones or teeth have been found in any of the caverns or alluvial deposits in which those of Elephants, Rhinoceroses, and Hippopotamuses occur in abundance; but in other regions their distribution at this age was far wider than at present, as they are known to have extended eastward to China (_T. sinensis_, Owen) and westwards over the greater part of the southern United States of America, from South Carolina to California. Lund also distinguished two species or varieties from the caves of Brazil, one of which appears identical with _T. americanus_. Thus we have no difficulty in tracing the common origin in the Miocene Tapirs of Europe of the now widely separated American and Asiatic species. It is, moreover, interesting to observe how very slight an amount of variation has taken place in forms isolated during such an enormous period of time.

[Illustration: FIG. 152.—The American Tapir (_Tapirus americanus_).]

The anatomy of the soft parts of the Tapirs[256] conforms to the general Perissodactyle type, as exemplified in the Rhinoceros and the Horse, although on the whole (as might have been expected) presenting a closer resemblance to the former. _T. americanus_ differs from _T. indicus_ by the absence, or at any rate the less development, of the intestinal valvulæ conniventes, the presence of a moderator band in the heart, the shape of the glans penis, and the more elongated cæcum, which is sacculated by four distinct longitudinal fibrous bands. The convolutions of the hemispheres of the brain of the Tapirs are simpler than in other Perissodactyles, thus tending to confirm the inferences which may be drawn from the skeleton and teeth as to the comparatively low or generalised organisation of these animals.

_Palæotapirus._—This name has been applied to an imperfectly known form from the Upper Eocene Phosphorites of Central France, which is regarded by Dr. Filhol as referable to this family.

_Family_ LOPHIODONTIDÆ.

Molars brachydont and bilophodont, those of the lower jaw with either straight or imperfectly crescentoid ridges; premolars smaller and usually simpler than the molars; last lower molar generally with a third lobe. Outer columns of upper molars conical or flattened. Digits usually as in the preceding family.

[Illustration: FIG. 153.—Right side of skull of _Hyracotherium leporinum_, from the London Clay. ½ natural size. (After Owen.) 3, Occiput; 7, sagittal crest; 11, frontals; 15, nasals; 21, maxilla; 22, premaxilla; _d_, mandibular condyle; _a_, aperture of facial nerve; _p_ 1-4, premolars; _m_ 1-3, molars.]

This family includes a number of more or less imperfectly known forms, all of which are extinct and apparently confined to the Eocene period, and ranging from the size of a Rabbit to that of a Rhinoceros. Although some of these appear to have died out without giving rise to more specialised forms, it is probable that this family contained the ancestral types from which most or all of the modern Perissodactyles have been derived. Only very brief mention can be made here of some of the leading genera. _Lophiodon_, of the Middle and Upper Eocene of Europe, with the dental formula, _i_ ³⁄₃, _c_ ¹⁄₁, _p_ ³⁄₃, _m_ ³⁄₃, includes the largest representatives of the family, and is generally regarded as a stock which has died out without giving rise to later forms. The ridges of the lower molars are straight, and the last of these teeth has a third lobe; while the second transverse ridge of the last upper premolar is usually incomplete; the outer columns of the upper molars are flattened, as in the next genus. _Hyrachyus_, of the Upper Eocene of the United States, and probably also occurring in the French Eocenes, is an allied genus, with four premolars and no third lobe to the last lower molar; the fourth upper premolar having the two ridges uniting internally to form a crescent. This genus has been regarded as the ancestor of the Rhinocerotic _Hyracodon_. The genus _Hyracotherium_ was established in 1839 by Owen for a small animal no larger than a Hare, the skull of which was found in the London Clay at Herne Bay. A more nearly perfect specimen, apparently of the same species, was afterwards (in 1857) described under the name of _Pliolophus vulpiceps_, of which the skull is figured in the accompanying woodcut. Other forms referable to the same genus have been obtained from the Wasatch Eocene of the United States, and were described by Professor Marsh under the name of _Eohippus_. There were four premolars, the fourth being unlike the molars, and in the upper jaw having only one inner cusp. The upper molars are of the general type of those of _Lophiodon_, but have conical outer columns, and the anterior transverse ridge imperfect, while the ridges of the lower molars are crescentoid. _Systemodon_ differs from _Hyracotherium_ by the absence of a diastema between the first and second premolars; it occurs in the Wasatch Lower Eocene of the United States. In _Pachynolophus_ (_Lophiotherium_, _Orotherium_, or _Orohippus_), which is common to the Middle and Upper Eocene of Europe and the Bridger Eocene of North America, the outer columns of the upper molars are flattened, and in some cases, at least, the last premolar resembles the molars, that of the upper jaw having two inner cusps.[257] This genus, indeed, so closely connects _Hyracotherium_ with the genera _Epihippus_ and _Anchilophus_ as to show that the distinction between the _Lophiodontidæ_ and _Palæotheriidæ_ is really an arbitrary one. _Epihippus_, of the Upper Eocene of the United States, has both the third and fourth upper premolars as complex in the molars, and is distinguished from _Anchilophus_ by the lower cusps and more imperfect transverse ridges of these teeth. The so-called _Orohippus agilis_ belongs to this genus. _Isectolophus_ is another American Eocene genus which may be provisionally placed in this family; it is regarded by Professors Scott and Osborn as connecting _Systemodon_ with the _Tapiridæ_; the fourth and probably the third upper premolar approximating in structure to the molars; the upper molars have conical outer columns. _Helaletes_ is another closely allied form, with similar premolars, but with the outer columns of the upper molars flattened.

[Illustration: FIG. 154.—Restoration of _Palæotherium_ (Upper Eocene). After Cuvier.]

_Family_ PALÆOTHERIIDÆ.

[Illustration: FIG. 155.—A half-worn right upper molar of _Palæotherium magnum_. (After Owen.) _f_, _f_, External surfaces of outer columns; _a_, postero-external column (metacone); _b_, antero-external column (paracone); _c_, postero-internal column (hypocone); _d_, antero-internal column (protocone); _i_, anterior intermediate column (protoconule); _e_, median valley; _g_, posterior valley.]

Molars (Fig. 155) brachydont, with the valleys between the ridges never filled with cement; upper premolars either simpler than or as complex as the molars; lower molars with crescentoid ridges, and the last of the series with or without a third lobe. Outer columns of upper molars flattened. Orbit (at least usually) confluent with temporal fossa. Three digits on each foot. This family includes extinct genera ranging from the Middle and Upper Eocene to the Miocene, and passes so gradually into the following one that the maintenance of the two can only be supported on the ground of convenience. The typical genus, _Palæotherium_, was made known to science in the early part of the present century by Cuvier, who restored the skeleton (Fig. 154) with a short neck like that of the Tapirs, although it has been subsequently found that the neck was considerably longer. This genus (which may be taken to include _Paloplotherium_) ranges from the Middle to the Upper Eocene of Europe, and usually has the full typical dentition, although the first premolar may disappear. The last lower molar has a third lobe; and in the typical forms the last premolar is as complex as the molars, the diastema is short, and the canines are not large. In other forms, however, the hinder ridge of the fourth upper premolar may be aborted. The first upper cheek-tooth is generally a well-developed tooth, which may have a deciduous predecessor. _Anchilophus_, of the Upper Eocene of Europe, and _Anchitherium_, of the Miocene of Europe and North America, connect the preceding forms with the _Equidæ_. In the latter genus there is the full number of teeth, the last lower molar has almost completely lost the third lobe of _Anchilophus_, and the surfaces of the two outer lobes of the upper molars (Figs. 157, 158) lack the median vertical ridges of that genus. In the American species of _Anchitherium_ (which have been described as _Mesohippus_ and _Miohippus_) the lateral digits are larger than in the European Middle Miocene _Anchitherium aurelianense_; a mere splint represents the fifth metacarpal, and the meso- and ento-cuneiform of the tarsus do not unite as they do in the latter.

_Family_ EQUIDÆ.

Molars hypsodont, with the outer columns of the upper ones flattened, the valleys completely filled with cement, and the enamel thrown into folds and plications; upper premolars as complex as molars, which they slightly exceed in size; ridges of lower molars crescentoid, and complicated by enamel-foldings; no distinct third lobe to last lower molar; summits of incisors with a central infolding of enamel. Orbit completely surrounded by bone. Digits three or one, but in the former case the median one is alone of functional importance; ulna and fibula incomplete; meso- and ento-cuneiform of tarsus united.

Such are the leading characters which serve to distinguish the existing Horses and their nearest fossil allies from the _Palæotheriidæ_. The Horse, as being the best known of the Perissodactyle Ungulates, is selected for a somewhat detailed description; but before proceeding to this it will be advisable to take a brief survey of the relations of the _Equidæ_ to the extinct forms already noticed, and also of the modifications of the family at present existing.

The earliest form which can be certainly included in this line of descent is the American Lower Eocene genus _Phenacodus_ (noticed below under the head of the suborder Condylarthra), in which there were five complete digits to the feet. From this form there is but a step to _Systemodon_ and _Hyracotherium_, in which the functional digits of the manus were reduced to four, as in _Pachynolophus_ (Fig. 156, _a_), although one species retained a rudiment of the metacarpal of the pollex.

[Illustration: FIG. 156.—Successive stages of modification of the feet of extinct forms of Horse-like animals (chiefly from Marsh), showing gradual reduction of the outer and enlargement of the middle toe (III). _a_, _Pachynolophus_ (Eocene); _b_, _Anchitherium_ (Early Miocene); _c_, _Anchitherium_ (Late Miocene); _d_, _Hipparion_ (Pliocene); _e_, _Equus_ (Pleistocene).]

The transition from these animals of the Eocene period to the Horses of modern times has been accompanied by a gradual increase in size. The diminutive _Hyracotherium_ of the Lower, and _Pachynolophus_ of the Middle and Upper Eocene were succeeded in the Miocene period by the forms to which the name of _Anchitherium_ has been given, of the size of sheep; these again in Pliocene times by _Hipparion_ and _Protohippus_, as large as the modern donkeys; and it is mainly in the Pleistocene period that _Equidæ_ occur which approach in size the existing Horse. Important structural modifications have also taken place, with corresponding changes in the mode of life of the animal. Thus the neck has become elongated, the skull altered in form, the teeth greatly modified, and the limbs have undergone remarkable changes. The last two require to be described more in detail.

[Illustration: FIG. 157.—_a_, Grinding surface of unworn molar tooth of _Anchitherium_; _b_, corresponding surface of unworn molar of young Horse; _c_, the same tooth after it has been some time in use. The uncoloured portions are the dentine or ivory, the shaded parts the cement filling the cavities and surrounding the exterior. The black line separating these two structures is the enamel or hardest constituent of the tooth.]

The teeth in the Eocene forms had, as mentioned above, the characteristic number of forty-four. This number has been retained throughout the series, at least theoretically; but one tooth on either side of each jaw, the anterior premolar, which in all the Eocene and Miocene species was well developed, persisting through the lifetime of the animal, is in all modern Horses rudimentary, functionless, and generally lost at an early period of life, evidently passing through a stage which must soon lead to its complete disappearance. The canines have also greatly diminished in size, and are rarely present in the female sex, so that practically a very large number of adult Horses of the present day have eight teeth less than the number possessed by their predecessors. The diastema or interval between the incisor and premolar teeth (of essential importance in the domesticated Horse to his master, as without it there would be no room for inserting the special instrument of subjugation to his commands, the bit) already existed in the earliest known forms, but has gradually increased in length. The incisors have undergone in comparatively recent times that curious change producing the structure more fully described hereafter, which distinguishes the Horse’s incisors from those of all other known animals, with the exception of the extinct _Macrauchenia_. Lastly, the molars have undergone a remarkable series of modifications, much resembling in principle those that have taken place in several other groups of herbivorous animals. Distinctions in form which existed between the premolars, at least in the anterior part of the series, and the true molars have gradually disappeared, the teeth becoming all very uniform in the shape and structure of their grinding surface. The crowns of all these teeth in the early forms were very short (see Fig. 158, _a_); there was a distinct constriction, or neck, between the crown and roots; and when the tooth was developing, as soon as the neck once rose fairly above the alveolar margin, the tooth remained permanently in this position. The term “brachydont” expresses this condition of teeth, the mode of growth of which may be illustrated by those of man. The free surface had two nearly transverse curved ridges, with valleys between (Fig. 157, _a_); but the valleys were shallow and had no deposit of cement filling them, the whole exposed surface of the unworn tooth being formed of enamel. When the ridges became worn down the dentine of the interior was exposed, forming islands surrounded by enamel. With the progress of time the crowns of the teeth gradually became longer, the valleys deeper, and the ridges not only more elevated but more curved and complex in arrangement. To give support to these high ridges and save them from breaking in use, the valleys or cavities between them became filled up to the top with cement, and as the crown wore down an admirable grinding surface consisting of patches and islands of the two softer substances, dentine and cement, separated by variously reduplicated and contorted lines of intensely hard enamel, resulted (Fig. 157, _c_). The crown continued lengthening until in the modern Horses it has assumed the form called “hypsodont” (Fig. 158, _b_). Instead of contracting into a neck, and forming roots, its sides continue parallel for a considerable depth in the socket, and as the surface wears away, the whole tooth slowly pushes up, and maintains the grinding edge constantly at the same level above the alveolus, much as in the perpetually growing Rodent’s teeth. But in existing Horses there is still a limit to the growth of the molar. After a length is attained which in normal conditions supplies sufficient grinding surface for the lifetime of the animal, a neck and roots are formed, and the tooth is reduced to the condition of that of the brachydont ancestor. It is perfectly clear that this lengthening of the crown adds greatly to the power of the teeth as organs of mastication, and enables the animals in which it has taken place to find their sustenance among the comparatively dry and harsh herbage of the open plains, instead of being limited to the more succulent vegetable productions of the marshes and forests in which their predecessors probably dwelt.

[Illustration: FIG. 158.—_a_, Outer view of second upper molar teeth of _Anchitherium_ (brachydont form); _b_, corresponding tooth of Horse (hypsodont form).]

The modifications of the limbs which took place _pari passu_ with those of the teeth must have been associated with increased speed, especially over firm and unyielding ground. Short, stout legs, and broad feet, with numerous toes, spreading apart from each other when the weight of the creature is borne on them, are sufficiently well adapted for plodding deliberately over marshy and yielding surfaces, and the Tapirs and the Rhinoceroses, which in the structure of the limbs have altered but little from the primitive Eocene forms, still haunt the borders of streams and lakes and the shady depths of the forests, as was probably the habit of their ancient representatives, while the Horses are all inhabitants of the open plains, for life in which their whole organisation is in the most eminent degree adapted. The length and mobility of the neck, position of the eye and ear, and great development of the organ of smell, give them ample means of becoming aware of the approach of enemies, while the length of their limbs, the angles the different segments form with each other, and especially the combination of firmness, stability, and lightness in the reduction of all the toes to a single one, upon which the whole weight of the body and all the muscular power are concentrated, give them speed and endurance surpassing that of almost any other animal. When surprised, however, they are by no means helpless, both fore and hind feet becoming at need powerful weapons of defence.

If we were not so habituated to the sight of the Horse as hardly ever to consider its structure, we should greatly marvel at being told of a mammal so strangely constructed that it had but a single toe on each extremity, on the end of the nail of which it walked or galloped. Such a conformation is without a parallel in the vertebrate series, and is one of the most remarkable instances of specialisation, or deviation from the usual type, in accordance with particular conditions of life. It is clear, both from the structure of the foot itself, and also by an examination of the intermediate forms, that this toe corresponds to the middle or third digit of the complete typical or pentadactyle foot; and there is very strong evidence to show that by a gradual concentration of all the power of the limb upon this toe, and the concurrent dwindling away and final disappearance of all the others, the present condition of the Horse’s foot has been produced.

_Protohippus._[258]—In this Lower Pliocene North American genus (also described as _Merychippus_) the cheek-teeth resemble those of the generalised species of _Equus_, but have shorter crowns; while the milk-molars approximate to the permanent molars of _Anchitherium_. Each foot has three digits.

[Illustration: FIG. 159.—Three right upper cheek-teeth of _Hipparion_. _a_, Antero-external column; _b_, postero-external column; _c_, postero-internal column, or posterior pillar; _d_, antero-internal column, or anterior pillar; _f_, posterior intermediate column; _i_, anterior intermediate column. (From the _Palæontologia Indica_.)]

_Hipparion._[259]—Upper cheek-teeth (Fig. 159), with the antero-internal column, or anterior pillar as it may be conveniently termed in this family, detached throughout the greater part of its height from the adjacent column. Either a single or three digits in each foot. First upper premolar large and persistent. This genus was very widely distributed in the Pliocene, occurring in Europe, Asia, and North America. In the typical European forms, and also in those of North America, there were three digits in the feet (Fig. 156, _d_); but in the Indian _H. antilopinum_ (separated by Cope as _Hippodactylus_) the lateral digits seem to have disappeared. There is some doubt whether or no _Hipparion_ should occupy a place in the direct ancestry of the Horse, and Professor Cope suggests that while in America the intermediate place between _Anchitherium_ and _Equus_ was held by _Protohippus_, in Europe the same position was occupied by _Hipparion_—a view which involves the dual origin of the Horses of the New and Old Worlds.

_Equus._[260]—Upper cheek-teeth with the anterior pillar (except in a very early stage of wear) joined by a narrow neck to the adjacent column (Fig. 157, _c_). Each foot with a single complete digit, but with remnants of the proximal portions of the second and fourth metapodials (Fig. 156, _e_); some extinct forms having claw-like rudiments of the terminal phalangeals of the lateral digits. First upper premolar very small or altogether absent in existing species, but in some fossil species larger and persistent; first lower premolar only occasionally developed in some fossil forms. Ears long. Tail long, with long hairs either at the end or throughout. A callosity on the inner side of the fore limb above the carpus.

_Fossil Species._—In the Pleistocene Horses of South America described as _Hippidium_, as well as in the closely allied ones from North America for which the name _Pliohippus_ has been proposed, the upper molars are shorter and more curved than in the existing species, while their anterior pillar is not longer antero-posteriorly than in _Hipparion_; the lateral claw-like hoofs persisting. Some of the European Pliocene species (like _E. stenonis_) agree with these species in the form of the grinding surface of the anterior pillar of the upper molars. In one of the species from the Lower Pliocene of India (_E. sivalensis_)—which was a contemporary of _Hipparion_—and in all the existing species, the grinding surface of the pillar in question is greatly elongated in the antero-posterior direction, as in Fig. 157, _c_.

Fossil remains of Horses are found abundantly in deposits of the most recent geological age in almost every part in America, from Eschscholtz Bay in the north to Patagonia in the south. In that continent, however, they became quite extinct, and no Horses, either wild or domesticated, existed there at the time of the Spanish conquest, which is the more remarkable as, when introduced from Europe, the Horses that ran wild proved by their rapid multiplication in the plains of South America and Texas that the climate, food, and other circumstances were highly favourable for their existence. The former great abundance of _Equidæ_ in America, their complete extinction, and their perfect acclimatisation when reintroduced by man, form curious but as yet unsolved problems in geographical distribution.

_Existing Species._—The existing species of the genus are the following:—

The Horse, _Equus caballus_, is distinguished from the others by the long hairs of the tail being more abundant and growing quite from the base as well as the end and sides, and also by possessing a small bare callosity on the inner side of the hind leg, just below the “hock” or heel joint, in addition to the one on the inner side of the fore limb above the carpus, common to all the genus. The mane is also longer and more flowing, and the ears are shorter, the limbs longer, the hoofs broader, and the head smaller.

Though the existing Horses are not usually marked in any definite manner, or only irregularly dappled, or spotted with light surrounded by a darker ring, many examples are met with showing a dark median dorsal streak like that found in all the other members of the genus, and even with dark stripes on the shoulders and legs indicating “the probability of the descent of all the existing races from a single dun-coloured, more or less striped, primitive stock, to which our horses still occasionally revert.”[261]

In Europe wild Horses were extremely abundant in the Neolithic or polished-stone period. Judging from the quantity of their remains found associated with those of the men of that time, the chase of these animals must have been among man’s chief occupations, and they must have furnished him with one of his most important food supplies. The characters of the bones preserved, and certain rude but graphic representations carved on bones or reindeers’ antlers, enable us to know that these Horses were rather small in size, and heavy in build, with large heads and rough shaggy manes and tails, much like, in fact, the present wild horses of the steppes of the south of Russia. They were domesticated by the inhabitants of Europe before the dawn of history, but it is doubtful whether the majority of the animals now existing on the Continent are derived directly from them, as it is more probable that they are descendants from Horses imported through Greece and Italy from Asia, derived from a still earlier domestication, followed by gradual improvement through long-continued attention bestowed on their breeding and training. Horses are now diffused by the agency of man throughout almost the whole of the inhabited parts of the globe, and the great modifications they have undergone in consequence of domestication and selective breeding are well exemplified by comparing such extreme forms as the Shetland pony, dwarfed by uncongenial climate, the thoroughbred racer, and the London dray-horse. In Australia, as in America, horses imported by the European settlers have escaped into the unreclaimed lands, and multiplied to a prodigious extent, roaming in vast herds over the plains where no hoofed animal ever trod before.

A wild Horse from Central Asia, named _E. prezevalskii_,[262] is described as having callosities on both limbs and broad hoofs like _E. caballus_; but the long hairs of the tail do not begin until about half way down its length. It also differs from _E. caballus_ in having a short erect mane and no forelock; neither is there any dorsal stripe. The ears are of moderate size; the whole body is of a whitish-gray, paler beneath, and reddish on the head and upper parts of the limbs. If rightly described this form would appear to be intermediate between the true Horses and the Asses.

The second species is the domestic Ass (_E. asinus_), and the wild Asses of Africa (_E. asinus_, var. _africanus_ and var. _somalicus_[263]). The domestic Ass, which is now nearly as widely diffused and useful to man as the Horse, was known in Egypt long before the latter, and is doubtless of African origin. The ears are long, the mane erect, the tail without long hairs at the base, and there are no callosities on the hind limbs. There is a dark dorsal stripe, and another across the shoulders; while the limbs are frequently banded. Of the wild forms the Nubian race (var. _africanus_) has distinct dorsal and shoulder stripes, but the rings on the limbs are often very indistinct; while in the Somali race the dorsal stripe is indistinct, and the shoulder stripe wanting, but the rings on the limbs are very boldly marked. Teeth and bones from a Pleistocene cavern deposit in Madras have been referred to _E. asinus_.

The Asiatic wild Asses, which roam in small herds in the open plains of Syria, of many parts of Persia, of the north-west of India, and the highlands of Tartary and Tibet, from the shores of the Caspian to the frontiers of China, differ from the last in being of a more rufous or isabelline colour, instead of pure gray, in wanting the dark streak across the shoulder, and having smaller ears. They have all a dark-coloured median dorsal stripe. Though it is considered probable by many zoologists that they form but a single species[264] (_E. hemionus_), they present such marked variations in size and form that they have commonly been divided into three—the Syrian Wild Ass (_E. hemippus_), the Onager (_E. onager_) from Persia, Baluchistan, the Punjab, Sind, and the desert of Kach, and the Kiang or Dzeggetai (_E. hemionus_) of the high table-lands of Tibet, where it is usually met with at an elevation of 15,000 feet and upwards above the sea-level. The last is considerably larger than either of the others, and differs from them in external appearance, having more the aspect of the horse. They are all remarkably swift, having been known to outstrip the fleetest Horse in speed.

[Illustration: FIG. 160.—The Quagga (_Equus quagga_).]

Lastly, there are four striped species, all inhabitants of Africa. These constitute the genus _Hippotigris_ of Hamilton-Smith, but they are not separable except by their coloration from the true Asses, and one of them, the Quagga (_E. quagga_), may be considered as intermediate. This animal was formerly met with in vast herds on the great plains of South Africa, between the Cape Colony and the Vaal River, but now, in common with most of the larger wild animals of that region, is becoming extremely scarce, owing to the encroachments of European civilisation, if, indeed, it is not already extinct. In length of ears and character of tail it more resembles the Horse than it does the Ass, although it agrees with the latter in wanting the callosity on the inner side of the hind leg, just below the hock, characteristic of the Horse. The colour of the head, neck, and upper parts of the body is reddish-brown, irregularly banded and marked with dark brown stripes, stronger on the head and neck and gradually becoming fainter until lost behind the shoulder. There is a broad dark median dorsal stripe. The under surface of the body, the legs, and tail are nearly white, without stripes. The crest is very high, surmounted by a standing mane, banded alternately brown and white. Though never really domesticated, Quaggas have occasionally been trained to harness. The accompanying figure is reduced from a painting made from one of a pair which were driven in Hyde Park in the early part of the present century. The name is an imitation of the shrill barking neigh of the animal—“ouag-ga, ouag-ga,” the last syllable very much prolonged. It must be remembered, however, in reading books of African travel that the same word is very commonly applied by hunters to Burchell’s Zebra.

Of the Zebras proper, the one which was first known to Europeans, and was formerly considered the most common, is the True Zebra (_E. zebra_), sometimes called the Mountain Zebra. It inhabits the mountainous regions of the Cape Colony; but now, owing to the advances of civilised man into its somewhat restricted range, it has become very scarce, and is even, like the Quagga, threatened with extermination at no distant date. The second species, Burchell’s Zebra (_E. burchelli_), still roams in large herds over the plains to the north of the Orange River, but in yearly diminishing numbers. Both species are subject to considerable individual variations in marking, but the following are the principal characters by which they can be distinguished.

[Illustration: FIG. 161.—True or Mountain Zebra (_Equus zebra_).]

_E. zebra_ (Fig. 161) is the smaller of the two (about 4 feet high at the shoulders), and has longer ears, a tail more scantily clothed with hair, and a shorter mane. The general ground colour is white, and the stripes are black; the lower part of the face is bright brown. With the exception of the abdomen and the inside of the thighs, the whole of the surface is covered with stripes, the legs having narrow transverse bars reaching quite to the hoofs, and the base of the tail being also barred. The outsides of the ears have a white tip and a broad black mark occupying the greater part of the surface, but are white at the base. Perhaps the most constant and obvious distinction between this species and the next is the arrangement of the stripes on the hinder part of the back, where there are a number of short transverse bands passing from the median longitudinal dorsal stripe towards, and sometimes joining with, the uppermost of the broad stripes which run obliquely across the haunch from the flanks towards the root of the tail. There is often a median longitudinal stripe under the chest.

[Illustration: FIG. 162.—Burchell’s Zebra (_Equus burchelli_).]

_E. burchelli_ (Fig. 162) is a rather larger and more robust animal, with smaller ears, a longer mane, and fuller tail. The general ground colour of the body is pale yellowish-brown, the limbs nearly white, the stripes dark brown or black. In the typical form they do not extend on to the limbs or the tail; but there is a great variation in this respect, even in animals of the same herd, some being striped quite down to the hoofs (this form has been named _E. chapmani_). There is a strongly marked median longitudinal ventral black stripe, to which the lower ends of the transverse side stripes are usually united, but the dorsal stripe (also strongly marked) is completely isolated in its posterior half, and the uppermost of the broad haunch stripes runs nearly parallel to it. A much larger proportion of the ears is white than in the other species. In the middle of the wide intervals between the broad black stripes of the flanks and haunches fainter stripes are generally seen.

_E. grevyi._—Under this name a Zebra has been described which was sent in 1882 to Paris from the Galla country, lying to the south of Abyssinia, the most northern locality in which Zebras have previously been met with. In many of its characters it resembles _E. zebra_, but the stripes are much finer and more numerous than in the typical examples of that species, and it has a strong, black, and isolated dorsal stripe. Even allowing for the great variations that are met with in the markings of animals of this group, the aberrant characters of this individual are quite sufficient to separate it specifically from the true Zebra of South Africa. Other similar specimens have been recently brought from the Somali country.

The flesh of the Zebras is relished by the natives as food, and their hides are very valuable for leather. Although the many attempts that have been made to break in and train these animals for riding or driving have sometimes been rewarded with partial success, they have never been domesticated in the true sense of the word.

There are thus at least seven modifications of the Horse type at present existing, sufficiently distinct to be reckoned as species by all zoologists, and easily recognised by their external characters. They are, however, all so closely allied that each will, at least in a state of domestication or captivity, breed with perfect freedom with any of the others. Cases of cross breeds are recorded between the Horse and the Quagga, the Horse and Burchell’s Zebra, the Horse and the Hemionus or Asiatic wild Ass, the common Ass and the Zebra, the common Ass and Burchell’s Zebra, the common Ass and the Hemionus, the Hemionus and the Zebra, and the Hemionus and Burchell’s Zebra. The two species which are perhaps the farthest removed in general structure, the Horse and the Ass, produce, as is well known, hybrids or Mules, which in some qualities useful to man excel both their progenitors, and in some countries, and for certain kinds of work, are in greater requisition than either. Although occasional instances have been recorded of female Mules breeding with the males of one or other of the pure species, it is doubtful if any case has occurred of their breeding _inter se_, although the opportunities of doing so must have been great, as Mules have been reared in immense numbers for at least several thousands of years. We may therefore consider it settled that the different species of the group are now in that degree of physiological differentiation which enables them to produce offspring with each other, but does not permit of the progeny continuing the race, at all events unless reinforced by the aid of one of the pure forms.

The several members of the group show mental differences quite as striking as those exhibited by their external form, and more than perhaps might be expected from the similarity of their cerebral organisation. The patience of the Ass, the high spirit of the Horse, the obstinacy of the Mule, have long been proverbial. It is very remarkable that, out of so many species, two only should have shown any aptitude for domestication, and that these two should have been from time immemorial the universal and most useful companions and servants of man, while all the others remain in their native freedom to this day. It is, however, still a question whether this really arises from a different mental constitution causing a natural capacity for entering into relations with man, or whether it may not be owing to their having been brought gradually into this condition by long-continued and persevering efforts when the need of their services was keenly felt. It is quite possible that one reason why most of the attempts to add new species to the list of our domestic animals in modern times have ended in failure is that it does not answer to do so in cases in which existing species supply all the principal purposes to which the new ones might be put. It can hardly be expected that Zebras and Quaggas fresh from their native mountains and plains can be brought into competition as beasts of burden and draught with Horses and Asses, whose naturally useful qualities have been augmented by the training of thousands of generations of progenitors.

Not unfrequently instances occur of domestic Horses being produced with a small additional toe with complete hoof, usually on the inside of the principal toe, and, though far more rarely, three or more toes may be present. These malformations are often cited as instances of reversion to the condition of some of the earlier forms of equine animals previously mentioned. Such explanations, however plausible they appear at first sight, are nevertheless very doubtful. All the feet of polydactyle horses which we have examined bear little resemblance to those of _Hipparion_ or _Anchitherium_, but look rather as if due to that tendency to reduplication of parts which occurs so frequently as a teratological condition, especially among domestic animals, and, whatever its origin, certainly cannot in many instances, as the cases of entire limbs superadded, or of six digits in man, be attributed to reversion.

_Anatomy._—The anatomical structure of the Horse has been described in great detail in several works devoted to the subject, which will be mentioned in the bibliography, though these have generally been written from the point of view of the veterinarian rather than of the comparative anatomist. The limits of the present work will only admit of the most salient points being indicated, particularly those in which the Horse differs from the other Ungulata. Unless otherwise specified, it must be understood that all that is stated here, although mostly derived from observation upon the Horse, applies equally well to the other existing members of the group.

[Illustration: FIG. 163.—Side view of skull of Horse, with the bone removed so as to expose the whole of the teeth. _PMx_, Premaxilla; _Mx_, maxilla; _Na_, nasal; _Ma_, malar or jugal; _L_, lachrymal; _Fr_, frontal; _Sq_, squamosal; _Pa_, parietal; _oc_, occipital condyle; _pp_, paroccipital process; _i¹_, _i²_, and _i³_³, the three incisors; _c_, the canine; _pm¹_, the situation of the rudimentary first premolar, which has been lost in the lower, but is present in the upper jaw; _pm²_, _pm³_, and _pm⁴_, the three fully developed premolars; _m¹_, _m²_, and _m³_, the three true molars.]

_Skeleton._—The skull (Fig. 163) as a whole is greatly elongated, chiefly in consequence of the immense size of the face as compared with the hinder or true cranial portion. The basal line of the cranium from the lower border of the foramen magnum to the incisor border of the palate is very nearly straight. The orbit, of nearly circular form, though small in proportion to the size of the whole skull, is distinctly marked, being completely surrounded by a strong ring of bone with prominent edges. Behind it, and freely communicating with it beneath the osseous bridge (the postorbital process of the frontal) forming the boundary between them, is the small temporal fossa occupying the whole of the side of the cranium proper, and in front is the great flattened expanse of the “cheek,” formed chiefly by the maxilla, giving support to the long row of cheek-teeth, and having a prominent ridge running forward from below the orbit for the attachment of the masseter muscle. The lachrymal occupies a considerable space on the flat surface of the cheek in front of the orbit, and below it the jugal or malar does the same. The latter sends a horizontal or slightly ascending process backwards below the orbit to join the under surface of the zygomatic process of the squamosal, which is remarkably large, and, instead of ending as usual behind the orbit, runs forwards to join the greatly developed postorbital process of the frontal, and even forms part of the posterior and inferior boundary of the orbit, an arrangement not met with in other mammals. The closure of the orbit behind distinguishes the skull of the Horse from that of the Rhinoceros and Tapir, and also from all of the Perissodactyles of the Eocene period. In front of the cerebral cavity, the great tubular nasal cavities are provided with well-developed turbinal bones, and are roofed over by very large nasals, broad behind, and ending in front in a narrow decurved point. The opening of the anterior nares is prolonged backwards on each side of the face between the nasals and the elongated slender premaxillæ. The latter expand in front, and are curved downwards to form the semicircular alveolar border supporting the large incisor teeth. The palate is narrow in the interval between the incisor and cheek-teeth, in which are situated the large anterior palatine foramina. Between the cheek-teeth it is broader, and it ends posteriorly in a rounded excavated border opposite the hinder edge of the penultimate molar. It is mainly formed by the maxillæ, as the palatines are very narrow. The pterygoids are delicate slender slips of bone attached to the hinder border of the palatines, and supported externally by, and generally ankylosed to, the rough pterygoid plates of the alisphenoid, with no pterygoid fossa between. They slope very obliquely forwards, and end in curved, compressed, hamular processes. There is a distinct alisphenoid canal for the passage of the internal maxillary or main branch of the external carotid artery. The base of the cranium is long and narrow; the alisphenoid is very obliquely perforated by the foramen rotundum, but the foramen ovale is confluent with the large foramen lacerum medium behind. The glenoid surface for the articulation of the mandible is greatly extended transversely, concave from side to side, convex from before backwards in front, and hollow behind, and is bounded posteriorly at its inner part by a prominent post-glenoid process. The squamosal enters considerably into the formation of the temporal fossa, and, besides sending the zygomatic process forwards, it sends down behind the meatus auditorius a post-tympanic process which aids to hold in place the otherwise loose tympano-periotic bone. Behind this the exoccipital gives off a very long paroccipital process. The periotic and tympanic are ankylosed together, but not with the squamosal. The former has a wide but shallow floccular fossa on its inner side, and sends backwards a considerable “pars mastoidea,” which appears on the outer surface of the skull between the post-tympanic process of the squamosal and the exoccipital. The tympanic forms a tubular meatus auditorius externus directed outwards and slightly backwards. It is not dilated into a distinct bulla, but ends in front in a pointed styliform process; and completely embraces the truncated cylindrical tympanohyal, which is of great size, in correspondence with the large development of the whole anterior arch of the hyoid. This consists mainly of a long and compressed stylohyal, expanded at the upper end, where it sends off a triangular posterior process. The basihyal is remarkable for the long, median, pointed, compressed “glossohyal” process, which it sends forward from its anterior border into the base of the tongue. A similar but less developed process is found in the Rhinoceros. The mandible is largely developed, especially the region of the angle, which is expanded and flattened, giving great surface for the attachment of the masseter muscle. The condyle is greatly elevated above the alveolar border; its articular surface is very wide transversely, and narrow and convex from before backwards. The coronoid process is slender, straight, and inclined backwards. The horizontal ramus, long, straight, and compressed, gradually narrows towards the symphysis, where it expands laterally to form with the ankylosed opposite ramus the wide, semicircular, shallow alveolar border for the incisor teeth.

The vertebral column consists of seven cervical, eighteen dorsal, six lumbar, five sacral, and fifteen to eighteen caudal vertebræ. There may be nineteen rib-bearing vertebræ, in which case five only will be reckoned as belonging to the lumbar series. The odontoid process of the atlas is wide, flat, and hollowed above, as in the Ruminants. The bodies of the cervical vertebræ are elongated, strongly keeled, and markedly opisthocœlous, or concave behind and convex in front. Their neural laminæ are very broad, the spines almost obsolete, except in the seventh, and the transverse processes not largely developed. In the trunk vertebræ the opisthocœlous character of the centrum gradually diminishes. The spinous processes of the anterior thoracic region are high and compressed. To these is attached the powerful elastic ligament, _ligamentum nuchæ_, or “paxwax,” which passing forwards in the middle line of the neck above the neural arches of the cervical vertebræ, to which it is also connected, is attached to the occiput and supports the weight of the head. The transverse processes of the lumbar vertebræ are long, flattened, and project horizontally outwards or slightly forwards from the arch. The metapophyses are moderately developed, and there are no anapophyses. The caudal vertebræ, except those quite at the base, are slender and cylindrical, without processes and without chevron-bones beneath. The ribs are eighteen or nineteen in number on each side, flattened, and united to the sternum by short, stout, tolerably well ossified sternal ribs. The sternum consists of six pieces; the anterior or presternum being extremely compressed, and projecting forwards like the prow of a boat. The segments which follow gradually widen, and the hinder part of the sternum is broad and flat.

As in all other Ungulates, there are no clavicles. The scapula is long and slender; the suprascapular border is rounded, and slowly and imperfectly ossified. The spine is very slightly developed; rather above the middle its edge is thickened and somewhat turned backwards, but it gradually subsides at the lower extremity without forming any acromial process. The coracoid process is a prominent rounded nodule. The humerus is stout and rather short, and has a double bicipital groove. The ulna is quite rudimentary, being only represented by little more than the olecranon. The shaft gradually tapers below, and is firmly ankylosed to the radius. The latter bone is of nearly equal width throughout. The three bones of the first row of the carpus (the scaphoid, lunar, and cuneiform) are subequal in size. The second row consists of a very broad and flat magnum, supporting the great third metacarpal, having to its radial side the trapezoid, and to its ulnar side the unciform, which are both small, and articulate distally with the rudimentary second and fourth metacarpals. The pisiform is large and prominent, flattened, and curved; articulating partly with the cuneiform and partly with the lower end of the radius. The large metacarpal is called in veterinary anatomy “cannon-bone”; the small lateral metacarpals, which gradually taper towards their lower extremities, and lie in close contact with the large one, are called “splint-bones.” The single digit consists of a moderate-sized proximal (_os suffraginis_, or large pastern), a very short middle (_os coronæ_, or small pastern), and a wide, semilunar, ungual phalanx (_os pedis_, or coffin-bone). There is a pair of large nodular sesamoids behind the metacarpo-phalangeal articulation, and a single large transversely extended sesamoid behind the joint between the second and third phalanx, called the “navicular bone.”[265]

The carpal joint, corresponding to the wrist of man, is commonly called the “knee” of the Horse, the joint between the metacarpal and the first phalanx the “fetlock,” that between the first and second phalanges the “pastern,” and that between the second and third phalanges the “coffin-joint.”

In the hind limb the femur is marked, as in other Perissodactyles, by the presence of a “third trochanter,” a flattened process, curving forwards, arising from the outer side of the bone, about one-third of the distance from the upper end. The fibula is reduced to a mere styliform rudiment of the upper end; its lower part being absent or completely fused with the tibia. The calcaneum has a long and compressed calcaneal process. The astragalus has a large flat articular surface in front for the navicular, and a very small one for the cuboid. The navicular and the external cuneiform bones are very broad and flat. The cuboid is small, and the internal and middle cuneiform bones are small and united together. The metapodials and phalanges resemble very closely those of the fore limb, but the principal metatarsal is more laterally compressed at its upper end than is the corresponding metacarpal. The joint between the femur and tibia, corresponding to the knee of man, is called the “stifle joint”; while that between the tibia and tarsus, corresponding to the ankle of man, is termed the “hock.” The bones and joints of the foot have the same names as in the fore limb. The Horse is eminently “digitigrade,” standing on the extremity of the single digit of each foot, which is kept habitually in a position approaching to vertical.

The muscles[266] of the limbs are modified from those of the ordinary mammalian type in accordance with the reduced condition of the bones and the simple requirements of flexion and extension of the joints, no such actions as pronation and supination, or opposition of digits, being possible or needed. The muscles, therefore, which perform these functions in other mammals are absent or rudimentary.

[Illustration: FIG. 164.—Section of foot of Horse. 1, Metacarpal bone; 2, first phalanx (_os suffraginis_); 3, second phalanx (_os coronæ_); 4, third or ungual phalanx (_os pedis_, or coffin-bone); 5, one of the upper sesamoid bones; 6, lower sesamoid or “navicular” bone; 7, tendon of anterior extensor of the phalanges; 8, tendon of superficial flexor (_fl. perforatus_); 9, tendon of deep flexor (_fl. perforans_); 10, suspensory ligament of fetlock; 11, inferior or short sesamoid ligament; 12, derma or skin of the foot, covered with hair, and continued into 13, the coronary cushion, 14, the podophyllous or laminar membrane, and 15, the keratogenous membrane of the sole; 16, plantar cushion; 17, hoof; 18, fatty cushion of fetlock.]

Below the carpal and tarsal joints the fore and hind limbs correspond almost exactly in structure as well as function. On the anterior or extensor surface of the limb a powerful tendon (7 in Fig. 164), that of the anterior extensor of the phalanges (corresponding to the _extensor communis digitorum_ of the arm and _extensor longus digitorum_ of the foot of man) passes down over the metacarpal bone and phalanges, to be inserted mainly into the upper edge of the anterior surface of the last phalanx or pedal bone. There is also a much smaller second extensor on the outer side of this in each limb, the lateral extensor of the phalanges. In the fore leg the tendon of this muscle (which corresponds with the _extensor minimi digiti_ of man) receives a slip from that of the principal extensor, and is inserted into the first phalanx. In the hind leg (where it is the homologue apparently of the _peroneus brevis_ of man) the tendon becomes blended with that of the large extensor.

A very strong ligamentous band behind the metapodium, arising from near the upper extremity of its posterior surface, divides into two at its lower end, and each division, being first connected with one of the paired upper sesamoid bones, passes by the side of the first phalanx to join the extensor tendon of the phalanges. This is called in veterinary anatomy the “suspensory ligament of the sesamoids,” or of the “fetlock” (10 in Fig. 164); but its attachments and relations, as well as the occasional presence of muscular fibres in its substance, show that it is the homologue of the short flexor muscle of other mammals, curiously modified both in structure and function to suit the requirements of the Horse’s foot. Behind or superficial to this are placed the two strong tendons of the long flexor muscles, the most superficial, or _flexor perforatus_ (8), dividing to allow the other to pass through, and then inserted into the middle phalanx. The _flexor perforans_ (9) is as usual inserted into the terminal phalanx. In the fore leg these muscles correspond with those similarly named in man. In the hind leg, the perforated tendon is a continuation of that of the plantaris, passing pulley-wise over the tuberosity of the calcaneum. The perforating tendon is derived from the muscle corresponding with the long flexor of man, and the smaller tendon of the oblique flexor (_tibialis posticus_ of man) is united with it.

The hoof of the Horse corresponds to the nail or claw of other mammals, but is so constructed as to form a complete and very solid case to the expanded termination of the toe, giving a firm basis of support formed of a nonsensitive substance, which is continually renewed by the addition of material from within as its surface wears away by friction against the ground. The terminal phalanx of the toe is greatly enlarged and modified in form to support this hoof, and the size of the internal framework of the foot is further increased by a pair of lateral fibro-cartilaginous masses attached on each side to the hinder edges of the bone, and by a fibro-cellular and adipose plantar cushion in the median part. These structures are all enclosed in the keratogenous membrane or “subcorneous integument,” a continuation of the ordinary derma of the limb, but extremely vascular, and having its superficial extent greatly increased by being developed into papillæ or laminæ. From this the horny material which constitutes the hoof is exuded. A thickened ring encircling the upper part, called coronary cushion (13), and the sole (15), are covered with numerous thickly set papillæ or villi, and take the greatest share in the formation of the hoof; the intermediate part constituting the front and side of the foot (14), corresponding with the wall of the hoof, is covered with parallel, fine longitudinal laminæ, fitting into corresponding depressions in the inner side of the horny hoof.

The horny hoof is divided into a wall or crust consisting of the front and sides, the flattened or concave sole, and the “frog,” a triangular median prominence, notched posteriorly, with the apex turned forwards, situated in the hinder part of the sole. It is formed of pavement epithelial cells, mainly grouped in a concentric manner around the vascular papillæ of the keratogenous membrane, so that a section near the base of the hoof, cut transversely to the long axis of these papillæ, shows a number of small circular or oval orifices, with cells arranged concentrically round them. The nearer the surface of the hoof, or farther removed from the seat of growth, the more indistinct the structure becomes.

Small round or oval plates of horny epidermis called “chestnuts,” growing like the hoof from enlarged papillæ of the skin, are found on the inner face of the fore limb, above the carpal joint, in all species of _Equidæ_, and in the Horse (_E. caballus_) alone similar formations occur near the upper extremity of the inner face of the metatarsus. Their use is unknown.

Behind the joint between the metapodium and the first phalanx is a prominence formed by the fatty cushion of the fetlock (18 in Fig. 164). On the middle of this is a small bare patch covered with thickened epidermis, the _ergot_ or spur, generally concealed beneath the long hair which grows around it. This is the functionless vestige of the large callous pad found in this situation in the Tapir, and in fact in all mammals in which this part reaches the ground in walking.

[Illustration: FIG. 165.—Longitudinal and transverse section of upper incisor of Horse. _p_, Pulp cavity; _d_, dentine or ivory; _e_, enamel; _c_, outer layer of cement; _c′_, inner layer of cement, lining _a_, the pit or cavity of the crown of the tooth.]

_Dentition._—The dentition of the Horse, when all the teeth are in place, is, as stated before, expressed by the formula _i_ ³⁄₃, _c_ ¹⁄₁, _p_ ⁴⁄₃, _m_ ³⁄₃ = 42. The incisors of each jaw are placed in close contact, forming a semicircle. The crowns are broad, somewhat awl-shaped, and of nearly equal size. They have all the great peculiarity, not found in the teeth of any other living mammal, of an involution of the external surface of the tooth (see Fig. 165) forming a deep fossa or pit, the bottom of which becomes partially filled up with cement. As the tooth wears, the surface, besides the external enamel layer as in an ordinary simple tooth, shows in addition a second inner ring of the same hard substance surrounding the pit, thus of course adding greatly to the efficiency of the tooth as an organ for biting tough, fibrous substances. This pit, generally filled in the living animal with particles of food, is conspicuous from its dark colour, and constitutes the “mark” by which the age of the horse is judged, as in consequence of its extending only to a certain depth, it becomes obliterated as the crown wears away, when the tooth assumes the character of an ordinary incisor, consisting only of a core of dentine surrounded by the external enamel layer. It is not quite so deep in the lower as in the upper teeth. The canines are either quite rudimentary or entirely absent in the female. In the male they are compressed, pointed, and smaller than the incisors, from which they are separated by a slight interval. The teeth of the cheek series are all in contact with each other, but separated from the canines by a considerable toothless space. The anterior premolars are quite rudimentary, often, especially in the lower jaw, not developed at all, and generally fall by the time the animal attains maturity, so that there are but six functional grinding teeth—three that have predecessors in the milk-dentition, and hence are considered as premolars, and three true molars, but otherwise, except the first and last of the series, not distinguishable in form or structure. These teeth in both upper and lower jaws are extremely long-crowned or hypsodont (Fig. 158), successive portions being pushed out as the surface wears away;—a process which continues until the animal becomes advanced in age. The enamelled surface is infolded in a complex manner (a modification of that found in other Perissodactyles, see Figs. 155, 167), the folds extending quite to the base of the crown, and the interstices being filled and the surface covered with a considerable mass of cement, which binds together and strengthens the whole tooth. As the teeth wear, the folded enamel, being harder than the other constituents—the dentine and cement—forms projecting ridges on the surface arranged in a definite pattern, which give it great efficiency as a grinding instrument (see Fig. 157, _b_ and _c_). The free surfaces of the upper teeth are quadrate, except the first and last, which are nearly triangular. The lower teeth are much narrower than the upper.

The milk dentition consists of _i_ ³⁄₃, _c_ ⁰⁄₀, _m_ ³⁄₃ = 24,—the canines and first or rudimentary premolars having apparently no predecessors. In form and structure they much resemble the permanent teeth, having the same characteristic enamel-foldings. Their eruption commences a few days after birth, and is complete before the end of the first year, the upper teeth usually appearing somewhat earlier than those of the lower jaw. The first teeth to appear are the first and second milk-molars (about five days), then the central incisor (from seven to ten days); this is followed by the second incisor (at one month), then by the third molar, and finally by the third incisor. Of the permanent teeth the first true molar appears a little after the end of the first year, followed by the second molar before the end of the second year. At about two and a half years the first premolar replaces its predecessor. Between two and a half and three years the first incisor appears. At three years the second and third premolars and the third true molar have appeared; at from three and a half to four years the second incisor; at four to four and a half years the canine; and, finally, at five years the third incisor, completing the permanent dentition. Up to this period the age of the horse is clearly shown by the state of the dentition, and for some time longer indications can be obtained from the wear of the incisor teeth, though this depends to a certain extent upon the hardness of the food or other accidental circumstances. As a general rule, the depression caused by the infolding of the surface of the incisor (the “mark”), is obliterated in the first or central incisor at six years, in the second at seven years, and in the third at eight years. In the upper teeth, as the depressions are deeper, this obliteration does not take place until about two years later. After this period no certain indications can be obtained of the age of the horse from the teeth.

_Digestive Organs._—The lips are flexible and prehensile. The membrane that lines them and the cheeks is quite smooth. The palate is long and narrow; its mucous surface has seventeen pairs of not very sharply defined oblique ridges, extending as far back as the last molar tooth, beyond which the velum palati extends for about 3 inches, having a soft corrugated surface, and ending posteriorly in an arched border without uvula. This embraces the base of the epiglottis, and shuts off all communication between the cavity of the mouth and the nasal passages, respiration being, under ordinary circumstances, carried on exclusively through the nostrils. Between the mucous membrane and the bone of the hard palate is a dense vascular and nervous plexus. The membrane lining the fauces is soft and corrugated. An elongated raised glandular mass, 3 inches long and 1 inch from above downwards, extending backwards from the root of the tongue along the side of the fauces, with openings on the surface leading into crypts with glandular walls, represents the tonsil. The tongue, corresponding to the general form of the mouth, is long and narrow. It consists of a compressed intermolar portion with a flat upper surface, broad behind and becoming narrower in front; and of a depressed anterior part rather shorter than the former, which is narrow behind but widens towards the evenly rounded apex. The dorsal surface generally is very soft and smooth. There are two large circumvallate papillæ near the base, rather irregular in form, about a quarter of an inch in diameter and half an inch apart. The conical papillæ are very small and close set, though longer and more filamentous on the intermolar portion. There are no fungiform papillæ on the dorsum, but a few not very conspicuous ones scattered along the sides of the organ.

Of the salivary glands the parotid is by far the largest; elongated in the vertical direction, and narrower in the middle than at either upper or lower extremity. Its upper extremity embraces the lower surface of the cartilaginous ear-conch; its lower end reaches the level of the inferior margin of the mandible, along the posterior margin of which it is placed. Its duct leaves the inferior anterior angle, at first descends a little, and runs forward under cover of the rounded inferior border of the mandibular ramus, then curves up along the anterior margin of the masseter muscle, becoming superficial, pierces the buccinator, and enters the mouth by a simple aperture opposite the middle of the crown of the third premolar tooth. It is not quite so thick as a goose-quill when distended, and nearly a foot in length.

The submaxillary gland is of very similar texture to the last, but much smaller; it is placed deeper, and lies with its main axis horizontal. It is elongated and slender, and flattened from within outwards. Its posterior end rests against the anterior surface of the transverse process of the atlas, from which it extends forwards and downwards, slightly curved, to beneath the ramus of the jaw. The duct which runs along its upper and internal border passes forwards in the usual course, lying in the inner side of the sublingual gland, to open on the outer surface of a distinct papilla, situated on the floor of the mouth, half an inch from the middle line, and midway between the lower incisor teeth and the attachment of the frænum linguæ. The sublingual is represented by a mass of glands lying just beneath the mucous membrane of the floor of the mouth on the side of the tongue, causing a distinct ridge, extending from the frænum backwards, and the numerous ducts opening separately along the summit of the ridge. The buccal glands are arranged in two rows parallel with the molar teeth. The upper ones are the largest, and are continuous anteriorly with the labial glands, the ducts of which open on the mucous membrane of the upper lip.

The stomach of the Horse is simple in its external form, with a largely developed right _cul de sac_, and is a good deal curved on itself, so that the cardiac and pyloric orifices are brought near together. The antrum pyloricum is small and not very distinctly marked off. The interior is divided by the character of the lining membrane into two very distinct portions, right and left. Over the latter the dense white smooth epithelial lining of the œsophagus is continued, terminating abruptly by a raised crenellated border. Over the right part (rather the larger portion) the mucous membrane has a grayish-red colour and a velvety appearance, and contains very numerous peptic glands, which are wanting in the cardiac portion. The œsophageal orifice is very small, and is guarded by a strong crescentic or rather horse-shoe-like band of muscular fibres, which is supposed to be the cause of the difficulty of vomiting in the Horse. The small intestine is of great length (80 to 90 feet), its mucous membrane being covered with numerous fine villi. The cæcum is of conical form, about 2 feet long and nearly a foot in diameter; its walls are sacculated, especially near the base, having four longitudinal fibrous bands; and its capacity is about twice that of the stomach. It lies with its base near the lower part of the abdomen, and its apex directed towards the thorax. The colon is about one-third the length of the small intestine, and very capacious in the greater part of its course. As usual, it may be divided into an ascending, transverse, and descending portion; but the middle or transverse portion is folded into a great loop, which descends as low as the pubis; so that the colon forms altogether four folds, generally parallel to the long axis of the body. The descending colon is much narrower than the rest, and not sacculated, and being considerably longer than the distance it has to traverse, is thrown into numerous folds.

The liver (Fig. 166) is tolerably symmetrical in its general arrangement, being divided nearly equally into segments by a well-marked umbilical fissure. Each segment is again divided by lateral fissures, which do not extend quite to the posterior border of the organ; of the central lobes thus cut off, the right is rather the larger, and has two fissures in its free border subdividing it into lobules. The extent of these varies, however, in different individuals, being not usually so marked as in the figure, which is from a fœtal specimen. The two lateral lobes are subtriangular in form. The Spigelian lobe is represented by a flat surface between the portal fissure and the posterior border, not distinctly marked off from the left lateral by a fissure of the ductus venosus, as this vessel is buried deep in the hepatic substance, but the caudate lobe is distinct and tongue-shaped, its free apex reaching nearly to the border of the right lateral lobe. In most works on the anatomy of the Horse this has been confounded with the Spigelian lobe of man. There is no gall-bladder (as in all other Perissodactyles), and the biliary duct enters the duodenum about 6 inches from the pylorus. The pancreas has two lobes or branches—a long one passing to the left and reaching the spleen, and a shorter right lobe. The principal duct enters the duodenum with the bile-duct, and there is often a second small duct which opens separately near to this.

[Illustration: FIG. 166.—Under surface of the liver of the Horse. _u_, Umbilical fissure; _ll_, left lateral lobe; _lc_, left central lobe; _rc_, right central lobe; _rl_, right lateral lobe; _s_, Spigelian lobe; _c_, caudate lobe.]

_Circulatory and Respiratory Organs._—The heart has the form of a rather elongated and pointed cone. There is one anterior vena cava, formed by the union of the two jugular and two axillary veins. The aorta gives off a large branch (the anterior aorta) very near its origin, from which arise—first, the left axillary, and afterwards the right axillary and the two carotid arteries.

Under ordinary circumstances the Horse breathes entirely by the nasal passages, the communication between the larynx and the mouth being closed by the velum palati. The nostrils are placed laterally, near the termination of the muzzle, and are large and very dilatable, being bordered by cartilages upon which several muscles act. Immediately within the opening of the nostril, the respiratory canal sends off on its upper and outer side a diverticulum or blind pouch (called “false nostril”) of a conical form, and curved, 2 to 3 inches in depth, lying in the notch formed between the nasal and premaxillary bones. It is lined by mucous membrane continuous with that of the nasal passage, but its use is not apparent. It is longer in the Ass than in the Horse. A similar structure is found in the Rhinoceros, and in a much more developed condition in the Tapir. Here may be mentioned the guttural pouches, large air sacs, diverticula from the Eustachian tubes, and lying behind the upper part of the pharynx. These are likewise found in other Perissodactyles, but their use is also still not clearly understood. The larynx has the lateral sacculi well developed, though entirely concealed within the alæ of the thyroid cartilage. The trachea divides into two bronchi, one for each lung.

_Nervous System._—The brain differs little, except in details of arrangement of convolutions, from that of other Ungulates. The cerebral hemispheres are rather elongated and subcylindrical, the olfactory lobes are large and project freely in front of the hemispheres, and the greater part of the cerebellum is uncovered. The eye is provided with a nictitating membrane or third eyelid, at the base of which the ducts of the Harderian gland open.

_Reproductive System._—The testes are situated in a distinct sessile or slightly pedunculated scrotum, into which they descend from the sixth to the tenth month after birth. The accessory generative glands are the two vesiculæ seminales, with the median third vesicle, or _uterus masculinus_, lying between them, the single bilobed prostate, and a pair of globular Cowper’s glands. The penis is large, cylindrical, with a truncated, expanded, flattened termination. When in a state of repose it is retracted by a muscle arising from the sacrum, within the prepuce, a cutaneous fold attached below the symphysis pubis.

The uterus is bicornuate. The vagina is often partially divided by a membraneous septum or hymen. The mammæ (as in other members of the suborder), are two, inguinally placed. The surface of the chorion is covered evenly with minute villi, constituting a diffuse non-deciduate placenta. The period of gestation is eleven months.

_Bibliography._—M. S. Arloing, “Organisation du pied chez le cheval,” _Ann. Sci. Nat._ 1867, viii. pp. 55-81; H. Burmeister, _Los caballos fosiles de la Pampa Argentina_, Buenos Ayres, 1875; Chanveau and Arloing, _Traité d’anatomie comparée des animaux domestiques_, Paris, 1871, and English edition by G. Fleming, 1873; E. Cuyer and E. Alix, _Le Cheval_, 1886; A. Ecker, “Das Europäische Wildpferd und dessen Beziehungen zum domesticirten Pferd,” _Globus_, Bd. xxxiv. Brunswick, 1878; Forsyth-Major, “Beiträge zur Geschichte der fossilen Pferde besonders Italiens,” _Abh. Schw. Pal. Ges._ iv. pp. 1-16, pt. iv.; George, “Études zool. sur les Hémiones et quelques autres espèces chevalines,” _Ann. Sci. Nat._ 1869, xii. p. 5; E. F. Gurlt, _Anatomische Abbildungen der Haussäugethiere_, 1824, and _Hand. der vergleich. Anat. der Haussäugethiere_, 2 vols. 1822; Huet, “Croisement des diverses espèces du genre cheval,” _Nouv. Archives du Muséum_, 2d sér. tom. ii. p. 46, 1879; Leisering, _Atlas der Anatomie des Pferdes_, Leipsic, 1861; J. M’Fadyean, _The Anatomy of the Horse_, 1884; O. C. Marsh, “Notice of New Equine Mammals from the Tertiary Formation,” _Am. Journ. of Science and Arts_, vol. vii. March 1874; Id. “Fossil Horses in America,” _Amer. Naturalist_, vol. viii. May 1874; Id. “Polydactyle Horses,” _Am. Journ. of Science and Arts_, vol. xvii. June 1879; Franz Müller, _Lehrbuch der Anatomie des Pferdes_, Vienna, 1853; R. Owen, “Equine Remains in Cavern of Bruniquel,” _Phil. Trans._ vol. clix. (1870), p. 535; W. Percivall, _The Anatomy of the Horse_, 1832; G. Stubbs, _Anatomy of the Horse_, 1766. F. H. Huth’s _Bibliographical Record of Hippology_ (1887) contains a list of nearly four thousand works on Horses and Equitation, published in the various languages of the civilised world.

_Family_ RHINOCEROTIDÆ.

Although the existing members of this family are readily distinguished from the other living representatives of the suborder by the simple crescentoid form assumed by the ridges of the lower cheek-teeth, yet it is exceedingly difficult to give a definition by which they can be distinguished from the _Lophiodontidæ_, from some members of which they are, indeed, probably derived. The outer columns of the upper molars (Fig. 167) are, however, so excessively flattened as to produce a continuous thick and nearly straight outer wall, which is often produced in advance of the anterior transverse ridge; both transverse ridges being but little curved, and intimately connected with the outer wall. The upper premolars are in most cases nearly or quite as complex as the molars, and the ridges of the lower cheek-teeth are crescentoid. The last lower molar has no third lobe. The height of the crowns of the cheek-teeth is variable. The skull is large, with the orbit confluent with the temporal fossa. There are either three or four digits in the manus, and three in the pes. One or more dermal horns are attached to the fronto-nasal region of the skull of existing forms, but these were wanting in some of the fossil species.

[Illustration: FIG. 167.—A partially worn second right upper molar of _Rhinoceros antiquitatis_. Letters as in Fig. 155 (p. 375), except _k_, which indicates a prolongation of the median valley. (After Owen.)]

_Rhinoceros._[267]—Incisors variable, reduced in number, often quite rudimentary, and early deciduous. Upper canines absent. Molar series, consisting of the full number of four premolars and three molars above and below, all in contact and closely resembling each other, except the first, which is much smaller than the rest and often deciduous; and the last, in which the hinder lobe is partly aborted, so that the contour of the crown is triangular. Head large, skull elongated, elevated posteriorly into a transverse occipital crest. No postorbital processes. Nasal bones large and stout, co-ossified, and standing out freely above the premaxillæ, from which they are separated by a deep and wide fissure; the latter small, generally not meeting in the middle line in front, often quite rudimentary. Tympanics small, not forming a bulla. Brain cavity very small for the size of the skull. Vertebræ: C 7, D 19-20, L 3, S 4, C about 22. Limbs stout, and of moderate length. Three completely developed toes, with distinct broad rounded hoofs on each foot (Fig. 151, p. 368), some fossil forms having a fourth in the manus. Eyes small. Ears of moderate size, oval, erect, prominent, placed near the occiput. Skin very thick, in many species thrown into massive folds. Hairy covering scanty. When one horn is present it is situated over the conjoined nasal bones; when two, the hinder one is over the frontals. These horns, which are of a more or less conical form and usually recurved, often grow to a great length (three or even four feet), and are composed of a solid mass of hardened epidermic cells growing from a cluster of long dermal papillæ. The cells formed on each papilla constitute a distinct horny fibre, like a thick hair, and the whole are cemented together by an intermediate mass of cells which grow up from the interspaces between the papillæ. It results from this that the horn has the appearance of a mass of agglutinated hairs, which, in the newly growing part at the base, readily fray out on destruction of the softer intermediate substance; but the fibres differ from true hairs in growing from a free papilla of the derm, and not within a follicular involution of the same.

[Illustration: FIG. 168.—A partially worn second right upper molar of (_A_) _Rhinoceros sondaicus_, and (_B_) _R. unicornis_. _k_, Fossette cut off from median valley; _m_, crotchet; _n_, crista, or combining-plate; _e_, anterior valley; _l_, anterior intermediate column. Other letters as in Fig. 155, p. 375.]

The large lower cutting teeth of the typical Rhinoceroses have been very generally regarded as incisors, but comparison with fossil allied types, in which three lower incisors and canines are present, leaves little doubt but that they are really canines. The upper molar teeth present some amount of specific variation; thus while one type (Fig. 168, _A_) has only a simple “crotchet” projecting from the posterior transverse ridge into the median valley, in others (Fig. 168, _B_) this crotchet joins a “crista,” or “combing-plate,” projecting from the outer wall to cut off a distinct fossette from the median valley. Occasionally, however (as in Fig. 167), the crotchet and combing-plate do not completely join, although the fossette is distinctly indicated. The first upper premolar may occasionally be preceded by a milk-tooth. The Rhinoceroses differ from the Horses and agree with the Tapirs in the direction of the cæcum.

The living species of _Rhinoceros_ are all animals of large size, but of little intelligence, generally timid indisposition, though ferocious when attacked and brought to bay, using the nasal horns as weapons, by which they strike and toss their assailant. Their sight is dull, but their hearing and scent are remarkably acute. They feed on herbage, shrubs, and leaves of trees, and, like so many other large animals which inhabit hot countries, sleep the greater part of the day, being most active in the cool of the evening or even during the night. They are fond of bathing and wallowing in water or mud. None of the species have been domesticated. Animals of the group have existed in both the Old and New Worlds since the latter part of the Eocene period. In America they all became extinct before the end of the Pliocene period. In the Old World their distribution has become greatly restricted, and they are no longer found in Europe and North Asia, but only in Africa and portions of the Indian and Indo-Malayan region.

_Existing Species._—The existing (as well as many of the extinct) species of Rhinoceroses naturally divide into three groups, which are regarded by some zoologists as of generic value.

_Rhinocerotic, or Typical Group._—The adults with a single large compressed incisor above on each side, and occasionally a small lateral one; below, a very small incisor and a very large, procumbent, pointed canine. Nasal bones pointed in front. A single nasal horn. Skin very thick, and raised into strong, definitely arranged ridges or folds.

[Illustration: FIG. 169.—Indian Rhinoceros (_Rhinoceros unicornis_). This figure, and also figures 170, 172, are reduced from drawings by J. Wolf, from animals living in the London Zoological Society’s Gardens.]

There are two well-marked species of one-horned Rhinoceroses. (1) The Indian Rhinoceros, _R. unicornis_ (Fig. 169) of Linnæus,[268] the largest and best known, from being the most frequently exhibited alive in England, is at present only met with in a wild state in the terai region of Nipal and Bhutan, and in the upper valley of the Brahmaputra or province of Assam, though it formerly had a wider range. The first Rhinoceros seen alive in Europe since the time when these animals, in common with nearly all the large remarkable beasts of both Africa and Asia, were exhibited in the Roman shows, was of this species. It was sent from India to Emmanuel, King of Portugal, in 1513; and from a sketch of it, taken in Lisbon, Albert Dürer composed his celebrated but rather fanciful engraving, which was reproduced in so many old books on natural history. Both in this and the following species the post-glenoid and post-tympanic processes of the squamosal bone of the skull unite below so as to completely surround the external auditory meatus. The molar teeth are hypsodont, and have a horizontal plane of wear; those of the upper jaw (Fig. 168, _b_) being characterised by the presence of a combing-plate joining the crotchet, and the absence of a distinct buttress at the antero-external angle. The stomach departs from the ordinary Perissodactyle type. The small intestine is beset over most of its surface with long and fine villi; and the Spigelian lobe of the liver is well developed. There is a gland behind the foot. Teeth from the Pleistocene of the Narbada valley in India apparently indicate the existence of the Indian Rhinoceros at that epoch. (2) The Javan Rhinoceros (_R. sondaicus_, Fig. 170) is a smaller form, readily distinguished by dental and internal characters, as well as by the different arrangement of the plications of the skin (as seen in the figures); the horn in the female appears to be very little developed, if not altogether absent. This species has a more extensive geographical range, being found in the Bengal Sunderbans near Calcutta, Burma, the Malay Peninsula, Java, Sumatra, and probably Borneo. The molar teeth have shorter crowns than in the preceding species, and wear into ridges; those of the upper jaw (Fig. 168, _a_) having no combing-plate, and a strongly marked buttress at the antero-external angle (not distinctly shown in the figure). The visceral anatomy, according to Beddard,[269] does not differ materially from that of the next species. In respect to its dentition and anatomical characters this species is indeed more nearly allied to the Sumatran than to the Indian Rhinoceros; and thereby indicates that the division of the existing Rhinoceroses into separate genera is not advisable.

[Illustration: FIG. 170.—Javan Rhinoceros (_Rhinoceros sondaicus_).]

_Ceratorhine Group._—The adults with a moderate-sized compressed incisor above, and a laterally placed, pointed, procumbent canine below, which is sometimes lost in old animals. Nasal bones narrow and pointed anteriorly. A well-developed nasal, and a small frontal horn separated by an interval. The skin thrown into folds, but these not so strongly marked as in the former group. The smallest living member of the family, the Sumatran Rhinoceros, _R. sumatrensis_, Cuvier, now represents this group. Its geographical range is nearly the same as that of the Javan species, though not extending into Bengal; but it has been found in Assam, Chittagong, Burma, the Malay Peninsula, Sumatra, and Borneo. So far as can be determined during the life of the type specimen, it appears that the hairy form from Chittagong, described as _R. lasiotis_, is only a variety of this species.[270] The molar teeth of the Sumatran Rhinoceros are almost indistinguishable from those of the Javan species, and reference has already been made to the resemblance between the visceral anatomy of these species.[271] The form of the stomach is very similar to that of the Horse. The liver (Fig. 171) has a comparatively large caudate lobe, but is chiefly remarkable for the peculiar shape of the Spigelian lobe, which mainly consists of a thin strip of tissue, 8 inches long, ¾ inch wide, and ¼ inch deep. The small intestine, in place of the villi of _R. unicornis_, has throughout the greater part of its length a uniform series of thin and nearly or quite continuous transverse foldings, like the valvulæ conniventes of the human small intestine. There is no gland behind the foot. The post-glenoid and post-tympanic processes of the squamosal do not unite below the auditory meatus. The presence of a lateral nasal diverticulum, like that of the Horses and Tapirs, has been verified only in this species, although it doubtless occurs in the others.

[Illustration: FIG. 171.—Posterior aspect of the liver of _Rhinoceros sumatrensis_. _rc_, Right central lobe; _rl_, right lateral lobe; _lc_, left central lobe; _ll_, left lateral lobe; _c_, caudate lobe; _sp_, Spigelian lobe. (From Garrod, _Proc. Zool. Soc._ 1873, p. 102.)]

_Atelodine Group._—In the adults the incisors and canines quite rudimentary or entirely wanting. Nasal bones thick, rounded and truncated in front. Well-developed anterior and posterior horns in close contact. Skin without any definite permanent folds.

The two well-marked existing species are peculiar to the African continent.

[Illustration: FIG. 172.—Common African Rhinoceros (_Rhinoceros bicornis_).]

The common Two-horned Rhinoceros, _R. bicornis_, is the smaller of the two, with a pointed prehensile upper lip, and a narrow compressed deep symphysis of the lower jaw. It ranges through the wooded and watered districts of Africa, from Abyssinia in the north to the Cape Colony, but its numbers are yearly diminishing, owing to the inroads of European civilisation, and especially of English sportsmen. It feeds exclusively upon leaves and branches of bushes and small trees, and chiefly frequents the sides of wood-clad rugged hills. Specimens in which the posterior horn has attained a length as great as, or greater than, the anterior have been separated under the name of _R. keitloa_, but the characters of these appendages are too variable to found specific distinctions upon. The Common African Rhinoceros is far more rarely seen in menageries in Europe than either of the three Oriental species, but one has lived in the gardens of the London Zoological Society since 1868. The molar teeth of this species are of the general type of those of _R. sondaicus_, having no combing-plate to join the crotchet in those of the upper jaw. The conch of the ear is much rounded at its extremity, and edged by a fringe of short hairs; while the nostrils are somewhat rounded. The eye is placed immediately below the posterior horn.[272] Both in this and the following species the post-glenoid and post-tympanic processes of the squamosal do not unite below the auditory meatus. Nothing is known of the anatomy of the soft parts of either of them.

Burchell’s or the Square-mouthed Rhinoceros (_R. simus_), sometimes called the White Rhinoceros, though the colour (dark slate) is not materially different from that of the last species, is the largest of the whole group, and differs from all the others in having a square truncated upper lip and a wide, shallow, spatulate symphysis to the lower jaw. In conformity with the structure of the mouth, this species lives entirely by browsing on grass, and is therefore more partial to open countries or districts where there are broad grassy valleys between the tracts of bush. It is only found in Africa south of the Zambesi, and of late years has become extremely scarce, owing to the persecutions of sportsmen; indeed, the time of its complete extinction cannot be far off. No specimen of this species has ever been brought alive to Europe. Mr. F. C. Selous[273] gives the following description of its habits from extensive personal observation:—

“The square-mouthed rhinoceros is a huge ungainly-looking beast, with a disproportionately large head, a large male standing 6 feet 6 inches at the shoulder. Like elephants and buffaloes they lie asleep during the heat of the day, and feed during the night and in the cool hours of early morning and evening. Their sight is very bad; but they are quick of hearing, and their scent is very keen; they are, too, often accompanied by rhinoceros birds, which, by running about their heads, flapping their wings, and screeching at the same time, frequently give them notice of the approach of danger. When disturbed they go off at a swift trot, which soon leaves all pursuit from a man on foot far behind; but if chased by a horseman they break into a gallop, which they can keep up for some distance. However, although they run very swiftly, when their size and heavy build is considered, they are no match for an average good horse. They are, as a rule, very easy to shoot on horseback, as, if one gallops a little in front of and on one side of them, they will hold their course, and come sailing past, offering a magnificent broadside shot, while under similar circumstances a prehensile-lipped rhinoceros will usually swerve away in such a manner as only to present his hind-quarters for a shot. When either walking or running, the square-mouthed rhinoceros holds its head very low, its nose nearly touching the ground. When a small calf accompanies its mother it always runs in front, and she appears to guide it by holding the point of her horn upon the little animal’s rump; and it is perfectly wonderful to note how in all sudden changes of pace, from a trot to a gallop or _vice versâ_, the same position is always exactly maintained. During the autumn and winter months (_i.e._ from March to August) the square-mouthed rhinoceros is usually very fat; and its meat is then most excellent, being something like beef, but yet having a peculiar flavour of its own. The part in greatest favour among hunters is the hump, which, if cut off whole and roasted just as it is in the skin, in a hole dug in the ground, would, I think, be difficult to match either for juiciness or flavour.”

The molar dentition is of the type obtaining in _R. unicornis_, so that in this respect _R. simus_ has the same relation to _R. bicornis_ as is presented by _R. unicornis_ to _R. sondaicus_. The ear-conch of the Square-mouthed Rhinoceros is very large, elongated, and pointed at its extremity, which bears only a slight tuft of hair; it is much expanded in the middle, and the lower portion has its edges united to form a short tube. The nostrils have a long slit-like aperture; and the eye is situated behind the posterior horn.

_Extinct Species._—Using the generic term _Rhinoceros_ in its widest signification, a very large number of fossil forms may be referred to it, the earliest of which date from the Upper Eocene (Oligocene) Phosphorites of Central France. Only a few of the more important of these types can, however, be even mentioned in this place.

In the Pliocene Siwaliks of India _R. sivalensis_ appears to have been the direct ancestor of _R. sondaicus_; while _R. palæindicus_ was probably nearly related to _R. unicornis_, although the upper molars had not developed a combing-plate.

_R. schleirmacheri_, of the Lower Pliocene of Europe, falls into the Ceratorhine group, although differing from _R. sumatrensis_ by the union of the post-glenoid and post-tympanic processes of the squamosal beneath the auditory meatus. The Middle Miocene _R. sansaniensis_ was a closely allied if not identical form.

The Atelodine group was very widely spread in past epochs. Thus the huge _R. platyrhinus_ of the Indian Pliocene, and the equally large _R. antiquitatis_ of the Pleistocene of Europe, were specialised forms with a dentition resembling that of _R. simus_, to which they were probably allied. An upper molar of _R. antiquitatis_—the so-called Tichorine, or Woolly Rhinoceros—is shown in the woodcut on p. 402. Of this species nearly whole carcases, with the thick woolly external covering, have been discovered associated with those of the Mammoth, preserved in the frozen soil of the north of Siberia. In common with some other extinct species it had a solid median wall of bone supporting the nasals, from which it is inferred that the horns were of a size and weight surpassing that of the modern species. In the Lower Pliocene of Attica _R. pachygnathus_ appears to have been closely allied to _R. bicornis_. Several species such as _R. leptorhinus_ (Fig. 173), _R. megarhinus_, and _R. etruscus_, occur in the European Pleistocene which do not present a marked relationship to any of the living forms. This group is also represented in the Pleistocene of Southern India by the small _R. deccanensis_ and _R. karnuliensis_.

In the Upper Miocene, or Lower Pliocene, of North America numerous Rhinoceroses with incisor teeth occur which have no nasal horn, although in those forms of which the limbs are known the fore feet resembled those of existing species in having only three digits. These species have been generically separated as _Aphelops_, but so closely do they resemble existing Rhinoceroses that at one time Professor Cope proposed to refer the hornless female of _R. sondaicus_ (described by Lesson as _R. inermis_) to the same genus. If these American types be included in _Rhinoceros_ there seems no valid reason for separating the European Lower Pliocene and Miocene forms described as _Aceratherium_, at least some of which have four digits in the manus. This group is represented in the Upper Eocene Phosphorites of France, and also by a very large species in the Pliocene of India. Lastly, _R. minutus_, of the Lower Miocene of France, and an allied North American species are distinguished by carrying a pair of very small horns placed transversely across the nasals, from which feature it has been proposed that they should be separated genetically as _Diceratherium_.

[Illustration: FIG. 173.—Skull of _Rhinoceros leptorhinus_, from the Pleistocene of Essex. About ⅛ natural size.]

_Extinct Generic Types._—The Tertiary deposits of different parts of the world have yielded remains of many extinct forms more or less closely related to the Rhinoceroses, and some of which should certainly be included in the same family; although others perhaps form the types of one or more distinct families. One of the most remarkable of these extinct types is the huge _Elasmotherium_, from the Pleistocene of Siberia, in which the dentition was reduced to two premolars and three molars on either side of each jaw. The structure of the skeleton is essentially rhinocerotic, the skull having an ossified nasal septum, and a huge frontal prominence for the support of a very large horn. The teeth are extremely hypsodont, with the enamel plicated to a remarkable degree, and unlike those of _Rhinoceros_. The genus is evidently a very specialised one.

The other genera we have to notice are more generalised types. Of these the North American _Hyracodon_, with the full typical number of teeth, and without nasal horn, appears to connect the Rhinoceroses with the Lophiodont _Hyrachyus_. The genera _Amynodon_ and _Metamynodon_ (Fig. 174), from the American Tertiaries, are forms allied to the Rhinoceroses, with the full number of incisors and canines, and the hinder lobe of the last upper molar not aborted. The lower canines are either upright, or less proclivous than in the Rhinoceroses; in _Metamynodon_ the premolars are reduced to ³⁄₂. Molar teeth from the Phosphorites of Central France, described under the name of _Cadurcotherium_, are constructed on the general plan of those of the Rhinoceroses, although distinguished by their extreme narrowness; this type of tooth being very similar to that found in _Homalodontotherium_ from Tertiary deposits in Patagonia. The latter has the full number of teeth, without any diastema in the series. Until we have some knowledge of the skeleton of these remarkable forms nothing definite can be said as to their serial position.

[Illustration: FIG. 174.—Right half of the palatal surface of the cranium of _Metamynodon planifrons_, from the Upper Miocene of North America. (After Scott and Osborn.)]

_Families_ LAMBDOTHERIIDÆ, CHALICOTHERIIDÆ, AND TITANOTHERIIDÆ.

These families contain a large number of more or less nearly related extinct types from Tertiary beds of both the Old and New Worlds, some of which present most remarkable deviations from the ordinary Ungulate structure. All are characterised by their brachydont molars, which depart widely from the normal lophodont type. The upper molars consist of four columns, of which the two external ones are expanded to form an outer wall; the posterior pair being connected in some cases by an oblique transverse ridge, while there may be traces of an anterior ridge. The premolars are simpler.

_Lambdotheriidæ._—This family is confined to the Upper Eocene and Miocene of North America, where it is represented by _Lambdotherium_, _Palæosyops_, and _Limnosyops_; it presents the normal type of foot structure, and all the genera except the first have the full complement of teeth. There were four digits in the manus. The last lower molar has a third lobe. _Limnosyops_ differs from _Palæosyops_ in having two inner columns to the last upper molar.

[Illustration: FIG. 175.—Anterior and distal aspects of a phalangeal bone of _Chalicotherium sivalense_. (From the _Palæontologia Indica_.)]

_Chalicotheriidæ._—The genus _Chalicotherium_, which is found in the Tertiaries of Europe, Asia, and North America, differs so remarkably in the structure of the feet from all other Ungulates that it has been proposed to regard it as the representative of a distinct order, Ancylopoda. The molars are, however, almost indistinguishable from those of the preceding and following families; while the cervical vertebræ and portions of the limbs are of a Perissodactyle type. On the other hand, the femur has lost its third trochanter; while the phalanges are strangely modified, the terminal ones forming long curved claws, while the others (Fig. 175) have strong ginglymoid distal articulations. These phalanges were, indeed, long regarded as referable to Edentates, being described in Europe as _Macrotherium_, and in the United States as _Morotherium_ and _Moropus_. _Ancylotherium_, of the Grecian Pikermi beds, is founded upon phalanges which indicate an allied genus. The Indian species of _Chalicotherium_ is distinguished by the loss of the incisors and the upper canine; while all the species want the first premolar.

_Titanotheriidæ._—This exclusively North American family includes gigantic forms closely allied to the _Lambdotheriidæ_, but with the last upper premolar as complex as the molars, and frequently with large bony protuberances in the nasal region. The best known genus, _Titanotherium_ (_Menodus_,[274] _Brontotherium_, _Symborodon_, _Allops_, etc.), may either have the full complement of teeth, or the incisors may be reduced to ²⁄₀. The canines and incisors are small, and there is no diastema when the full dental series is developed. The skull is very like that of the Rhinoceroses; but has a transverse pair of large bony prominences on the nasal region, varying considerably in shape and size in the different species, which in the living animal were probably covered with horny sheaths. The third trochanter of the femur was aborted. These huge animals—inferior in size only to the Elephant—appear to have been abundant in the United States during the Miocene period.

_Family_ MACRAUCHENIIDÆ.

This extinct South American family is best known by the genus _Macrauchenia_, as represented by _M. patachonica_ and _M. boliviensis_, which are apparently from Pleistocene formations. They are very singular and specialised forms, quite out of the line of descent of any of the existing Perissodactyles, and the steps by which they are connected with the rest of the group have not yet been discovered. Of the larger species, _M. patachonica_, the skeleton is completely known. It had the full number of forty-four teeth, forming an almost uninterrupted series. The cervical vertebræ resemble those of the Camels in the position of the vertebrarterial canal, but the ends of the centra are flat, and not opisthocœlous as in the allied forms. In some of the limb characters it resembles the _Equidæ_, but in the articulation of the fibula with the calcaneum it agrees with the Artiodactyles. The structure of the feet is, however, distinctly Perissodactylate, there being three toes on each. The teeth approximate to a Rhinocerotine structure; and the incisors have an infolding of the enamel of their crowns, as in those of the Horses. The nares open on the top of the skull, and it is probable that the muzzle was produced into a short proboscis. Several other South American forms have been referred to this family, some of which have received distinct generic names, but further evidence is required before many of them can be accepted. Possibly _Homalodontotherium_ should be placed here.

_Family_ PROTEROTHERIIDÆ.

_Proterotherium._—Here may be noticed certain very remarkable Perissodactyles from the South American Tertiaries, for which the name _Proterotherium_ has been proposed. The cheek-teeth are so like those of _Anchitherium_ that they have been described under that name. The upper jaw has one pair of canine-like incisors and no canines, while the lower jaw carries two pairs of incisors. In the skull the orbits were completely closed, as in the Horses. The feet were tridactyle, like those of _Hipparion_, but the tarsus was constructed on an Artiodactyle type.

SUBUNGULATA.

By far the greater number of the Subungulata are extinct, and of many of those whose former existence has been revealed, chiefly by the labours of the American palæontologists, our knowledge is at present necessarily imperfect, though daily extending. It will only be possible here to give details of some of the more interesting or best-known forms.

The characters by which the skeleton of the feet of the Subungulata are distinguished from those of the Ungulata Vera have been already mentioned on p. 275. In addition to these it may be observed that the feet frequently have five functional digits, and may be plantigrade; while the upper surface of the astragalus is generally flattened, instead of presenting the strongly-marked pulley-like ridges and groove so characteristic of the Ungulata Vera.

_Suborder_ HYRACOIDEA.

_Family_ HYRACIDÆ.

[Illustration: FIG. 176.—_Hyrax capensis._]

This division is constituted to receive a single family of mammals, the affinities of which have long constituted a puzzle to zoologists. They were first placed among the Rodents, to which animals their small size and general appearance and habits give them much superficial resemblance. Cuvier’s investigations into their anatomical structure, and especially their dental characters, led him to place them among the Ungulates, near the genus _Rhinoceros_, a position long accepted by many zoologists. Further knowledge of their organisation and mode of development caused Milne-Edwards, Huxley, and others to disassociate them from this connection, and, failing to find any agreement with any other known forms, to place them in an order entirely apart. Palæontology has thrown no light upon the affinities of this anomalous and isolated group, as no extinct animals possessing their distinctive characters have as yet been discovered.

[Illustration: FIG. 177.—Skull and dentition of _Dendrohyrax dorsalis_. × ⅔.]

The dentition, according to the usual interpretation, consists only of incisors and molars, the formula in all known species being _i_ ¹⁄₂, _c_ ⁰⁄₀, _p_ ⁴⁄₄, _m_ ³⁄₃. The upper incisors have persistent pulps, and are curved longitudinally, forming a semicircle as in Rodents. They are, however, not flattened from before backwards as in that order, but prismatic, with an antero-external, an antero-internal, and a posterior surface, the first two only being covered with enamel; their apices are consequently not chisel-shaped, but sharp pointed. They are preceded by functional, rooted milk-teeth. The outer lower incisors, which should perhaps be regarded rather as canines, have long tapering roots, but not of persistent growth. They are straight, procumbent, with awl-shaped, trilobed crowns. Behind the incisors is a considerable diastema. The molars and premolars are all contiguous, and formed almost exactly on the pattern of some of the Perissodactyle Ungulates. The hyoid arch is unlike that of any known mammal. The dorsal and lumbar vertebræ are very numerous, 28 to 30, of which 21 or 22 bear ribs. The tail is extremely short. There are no clavicles. In the fore foot the three middle toes are subequally developed, the fifth is present, but smaller, and the hallux is rudimentary, although, in one species at least, all its normal bones are present. The ungual phalanges of the four outer digits are small, somewhat conical, and flattened in form. The carpus has a distinct os centrale. There is a slight ridge on the femur in the place of a third trochanter. The fibula is complete, thickest at its upper end, where it generally ankyloses with the tibia. The articulation between the tibia and astragalus is more complex than in other mammals, the end of the malleolus entering into it. The hind foot is very like that of _Rhinoceros_, having three well-developed toes. There is no trace of a hallux, and the fifth metatarsal is represented only by a small nodule. The ungual phalanx of the inner (or second) digit is deeply cleft, and has a peculiar long curved claw, the others have short broad nails. The stomach is formed upon much the same principle as that of the Horse or Rhinoceros, but is more elongated transversely and divided by a constriction into two cavities—a large left _cul de sac_, lined by a very dense white epithelium and a right pyloric cavity, with a very thick, soft, vascular lining. The intestinal canal (Fig. 178) is long, and has an arrangement perfectly unique among mammals, indeed among vertebrated animals, for, in addition to the ordinary short, but capacious and sacculated cæcum (_cm_) at the commencement of the colon, there is, lower down, an additional pair of large, conical, pointed, supplemental cæca (_c_). The liver is much subdivided, and there is no gall-bladder. The brain resembles that of the typical Ungulates far more than the Rodents. The testes are permanently abdominal. The ureters open into the fundus of the bladder, as in some Rodents. The female has six teats, of which four are inguinal and two axillary; and the placenta is zonary, as in the Elephant and Carnivora.

[Illustration: FIG. 178.—Diagrammatic view of the alimentary canal of _Hyrax capensis_, the intestines being somewhat abbreviated. _d_, Duodenum; _i_, ileum; _cm_, cæcum; _c_, supplemental colic cæca; _r_, rectum.]

There are two distinct forms of Hyrax, differing both in structure and habits, which may be accorded generic rank.

_Hyrax._[275]—Molar teeth having the same pattern as those of _Rhinoceros_. Interval between upper incisors less than the width of the teeth. Lower incisors slightly notched at the cutting edge. Vertebræ: C 7, D 22, L 8, S 6, C 6. Of this form the earliest known species, _H. capensis_ (Fig. 176) is the type. There are several other species, as _H. habessinicus_ and _syriacus_, from Eastern Africa and Syria. They inhabit mountainous and rocky regions, and live on the ground.

_Dendrohyrax._[276]—Molar teeth having the same pattern as _Palæotherium_ (except that the third lower molar has but two lobes). Interval between upper incisors exceeding the width of the teeth. Lower incisors with very distinctly trilobed crowns. Vertebræ: C 7, D 21, L 7, S 5, C 10. The members of this section frequent the trunks and large branches of trees, sleeping in holes. There are several species, not distinctly defined, from western and south Africa, as _D. arboreus_ and _D. dorsalis_. The members of both groups appear to have a power like that possessed by the Lizards called Geckos of clinging to vertical surfaces of rocks and trees by the soles of their feet.

It should be added that some writers separate three of the African species usually included in _Hyrax_ (viz. _H. bocagei_, _H. bakeri_, and _H. blainvillei_) under the designation of _Heterohyrax_.[277]

_Suborder_ PROBOSCIDEA.

This name has been appropriated to a well-marked group of animals, presenting some very anomalous characters, allied in many respects to the typical Ungulata, but belonging neither to the Artiodactyle nor Perissodactyle type of that order. It has been thought that they possess some, though certainly not very close, affinities with the Rodentia, and also with the Sirenia. It is certain, however, that the two species of Elephant, which are the sole living representatives of the group, stand quite alone among existing mammals, differing widely from all others in many points of their structure. In some respects, as the skull, proboscis, and dentition, they are highly specialised; but in others, as in the presence of two anterior venæ cavæ and in the structure of the limbs, they retain a low or generalised condition. A considerable series of extinct forms, extending back through the Pliocene and Miocene epochs, show the same type under different modifications, and in still more generalised outlines; and certain forms from the Eocene of North America, if their affinities are rightly interpreted, appear to link the true Proboscidea to some unknown primitive type of Ungulata.

The following are the principal characters common to existing, and, by inference, to the extinct, Proboscidea. The nose extended into a long, muscular, very flexible and prehensile proboscis, at the end of which the nostrils are situated, and from which the name given to the group is derived. The teeth consisting of ever-growing incisors of very great size, but never exceeding one pair in each jaw, and often present in one jaw only; no canines; large and transversely ridged molars. No clavicles. Limbs strong, the upper segment, especially in the hind limb, the longer. Radius and ulna distinct, the latter articulating extensively with the carpus. Fibula and tibia distinct. Astragalus very flat on both surfaces. Manus and pes short, broad, and massive, each with five toes, though the outer pair may be more or less rudimentary, all encased in a common integument, though with distinct, broad, short hoofs. Third digit the largest. Two anterior venæ cavæ entering the right auricle. Stomach simple. A capacious cæcum. Testes permanently abdominal. Uterus bicornuate. Placenta non-deciduate and zonary. Mammæ two, pectoral.

With regard to the teeth, the incisors,[278] which project largely out of the mouth, and are commonly called “tusks,” are of an elongated conical form, and generally curved. They are composed mainly of solid dentine, the fine elastic quality and large mass of which renders it invaluable as “ivory” for commerce and the arts. A peculiarity of the dentine of most Proboscidea is that it shows, in transverse fractures or sections, striæ proceeding in the arc of a circle from the centre to the circumference in opposite directions, and forming by their decussations curvilinear lozenges, as in the “engine-turning” of the case of a watch. The enamel-covering in existing species is confined to the extreme apex, and very soon wears off, but in some extinct species it forms persistent longitudinal bands of limited breadth. The tusks have small milk-predecessors, shed at an early age.

The molar teeth present a remarkable series of modifications, from the comparatively simple form in _Dinotherium_, with two or three strongly pronounced transverse ridges and a normal mode of succession, to the extremely complex structure and anomalous mode of replacement found in the true Elephants. The intermediate conditions occur in the various species of _Mastodon_. In this genus the enamel-covered transverse ridges of each tooth are generally more numerous than in _Dinotherium_, and often complicated by notches dividing their edge or by accessory columns attached to them, but in the unworn tooth they stand out freely on the surface of the crown, with deep valleys between (Fig. 179, I). In the Elephants the ridges are still further increased in number, and consequently narrower from before backwards, and are greatly extended in vertical height, so that, in order to give solidity to what would otherwise be a laminated or pectinated tooth, it becomes necessary to envelop and unite the whole in a large mass of cement, which completely fills up the valleys, and gives a general smooth appearance to the organ when unworn; but as the wear consequent upon the masticating process proceeds, the alternate layers of tissue of different hardness—cement, dentine, and enamel—which are disclosed upon the surface form a fine and very efficient triturating instrument. The modification of the tooth of a Mastodon into that of an Elephant is therefore precisely the same in principle as that of the molar of a Palæotherium into that of a Horse, or of the corresponding tooth of one of the primitive Artiodactyles into that of an Ox. The intermediate stages, moreover, even in the present state of our knowledge, are so numerous that it is not possible to draw a definite line between the two types of tooth structure (see Fig. 179, I, II, III, IV).

[Illustration: FIG. 179.—Longitudinal sections of the crown of a molar tooth of various Proboscideans, showing stages in the gradual modification from the simple to the complex form. I, _Mastodon americanus_; II, _Elephas insignis_; III, _Elephas africanus_; IV, _Elephas primigenius_. The dentine is indicated by transverse lines, the cement by a dotted surface, and the enamel is black.]

As regards the mode of succession, that of modern Elephants is, as before mentioned, very peculiar. During the complete lifetime of the animal there are but six molar teeth on either side of each jaw, with occasionally a rudimentary one in front, completing the typical number of seven. The last three represent the true molars of ordinary mammals; those in front appear to be milk-molars, which are never replaced by permanent successors, but the whole series gradually moves forwards in the jaw, and the teeth become worn away and their remnants cast out in front, while development of others proceeds behind. The individual teeth are so large, and the processes of growth and destruction by wear take place so slowly, that not more than one, or portions of two, teeth are ever in place and in use on either side of each jaw at one time, and the whole series of changes coincides with the usual duration of the animal’s life. On the other hand, the Dinotherium, the opposite extreme of the Proboscidean series, has the whole of the molar teeth in place and use at one time, and the milk-molars are vertically displaced by premolars in the ordinary fashion. Among Mastodons transitional forms occur in the mode of succession as well as in structure, many species showing a vertical displacement of one or more of the milk-molars, and the same has been observed in one extinct species of Elephant (_E. planifrons_) as regards the posterior of these teeth.

All known Proboscideans are animals of comparatively large dimensions, and some are the most colossal of land mammals. The head is of great proportionate size; and, as the brain case increases but little in bulk during growth, while the exterior wall of the skull is required to be of great superficial extent to support the trunk and the huge and ponderous tusks, and to afford space for the attachment of muscles of sufficient size and strength to wield the skull thus heavily weighted, an extraordinary development of air-cells takes place in the cancellous tissue of nearly all the bones of the cranium (Fig. 180). These cells are not only formed in the walls of the cranium proper, but are also largely developed in the nasal bones and upper part of the premaxillæ and maxillæ, the bones forming the palate and the basicranial axis, and even extend into the interior of the ossified mesethmoid and vomer. Where two originally distinct bones come into contact, the cells pass freely from one to the other, and almost all the sutures become obliterated in old animals. The intercellular lamellæ in the great mass which surrounds the brain cavity superiorly and laterally mostly radiate from the inner to the outer table, but in the other bones their direction is more irregular. Like the similar but less developed air-cells in the skulls of many other mammals, they all communicate with the nasal passages, and they are entirely secondary to the original growth of the bones, their development having scarcely commenced in the new-born animal, and they gradually enlarge as the growth of the creature proceeds towards maturity. The nasal bones are very short, and the anterior narial aperture is situated high in the face. The zygomatic arch is slender and straight, the jugal bone being small, and forming only the middle part of the arch, the anterior part of which (unlike that of typical Ungulates) is formed only by the maxilla. The maxillo-turbinals are but rudimentary, the elongated proboscis supplying their place functionally in warming and clearing from dust the inspired air.

[Illustration: FIG. 180.—A vertical section of the skull of the African Elephant (_Elephas africanus_) taken to the left of the middle line, and including the vomer (_Vo_) and the mesethmoid (_ME_). _an_, Anterior, and _pn_, posterior narial aperture. ¹⁄₁₂ natural size. (From Flower’s _Osteology of the Mammalia_.)]

The neck is very short. The limbs are long and stout, and remarkable for the great length of the upper segment (especially the femur) as compared with the distal segment, the manus, and pes. It is owing to this and the vertical position of the femur that the knee-joint in the hind leg is placed much lower, and is more conspicuous externally than in most quadrupedal mammals; and this having been erroneously compared with the hock-joint or ankle of typical Ungulates, the popular fallacy that the joints of the Elephant’s leg bend in a contrary direction to that of other mammals has arisen. There is no round ligament in the hip-joint, or third trochanter to the femur. The radius and ulna are distinct, though fixed in a crossed or prone position. The fibula also is quite distinct from the tibia. The feet are short and broad, the carpal and tarsal bones being very square, with flattened surfaces for articulation; the astragalus especially differs from that of typical Ungulates in its flatness, in the absence of a distinct pulley-like articular surface at either extremity, and in having no articular facet for the cuboid. The fibula articulates with the calcaneum, as in Artiodactyles. Of the five toes present on each extremity (see Fig. 98), the middle one is somewhat the largest, and the lateral ones smallest, and generally wanting (especially in the hind foot) the complete number of phalanges. The ungual phalanges are all small, irregular in form, and late in ossification. The whole are encased in a common integument, with a flat, subcircular, truncated sole, the only external indication of the toes being the broad oval nails or hoofs arranged in a semicircle around the front edge of the sole. The hind foot is smaller and narrower than the front. The liver is small and simple, and there is no gall-bladder. In form the brain resembles that of the Rodents and other lower orders of mammals, the cerebellum being entirely behind and uncovered by the cerebrum, but the hemispheres of the latter are richly convoluted.

The Proboscidea are exclusively vegetable feeders, living chiefly on leaves and young branches of forest trees and various kinds of herbage, which they gather and convey to their mouth by the very mobile proboscis, an organ which combines in a marvellous manner strength with dexterity of application, and is a necessary compensation for the shortness and inflexibility of the neck, as by it many of the functions of the lips of other animals are performed. By its means the Elephant is enabled to drink without bending the head or limbs; the end of the trunk being dipped into the stream or pool, a forcible inspiration fills the two capacious air-passages in its interior with water, which, on the tip of the trunk being turned upwards and inserted into the mouth, is ejected by a blowing action, and swallowed; or if the animal wishes to refresh and cool its skin, it can throw the water in a copious stream over any part of its surface. Elephants can also throw dust and sand over their bodies by the same means and for the same purpose, and wild animals have been frequently observed fanning themselves with leafy boughs held in the trunk. The species are at present limited in their geographical distribution to the Ethiopian and Oriental regions, but they formerly had a far more extensive range.

_Family_ ELEPHANTIDÆ.

Cheek-teeth succeeding one another in an arc of a circle, and portions of only two, or at most three, of the hinder teeth in use at any one time. Premolars frequently lost, and in any case of no functional importance.

_Elephas._[279]—Dentition: _i_ ¹⁄₀, _c_ ⁰⁄₀, _dm_ ³⁄₃, _m_ ³⁄₃ = 26. The incisors variable, but usually of very large size, especially in the male sex, directed somewhat outwards, and curved upwards, without enamel except on the apex before it is worn. The molars composed of numerous flattened enamel-covered plates or ridges of dentine, projecting from a common many-rooted base, surrounded and united together by cement, and extending straight across the crown, without (in most forms) any median division into inner and outer columns. The number of plates increases from the anterior to the posterior molar in regular succession, varying in the different species, but the third and fourth (or the last milk-molar and the first true molar), and these only, have the same number of ridges, which always exceeds five. Premolars nearly always wanting. Skull of adult very high and globular. Mandible ending in front in a short, deflected, and spout-like symphysis. Vertebræ: C 7, D 19-21, L 3-4, S 4, C 26-33.

The existing species of the genus differ so much that they have been referred by some writers to distinct genera; fossil forms show, however, such a transition from the one to the other that it is scarcely possible to regard them even as the representatives of distinct groups.

[Illustration: FIG. 181.—Grinding surface of a half-worn lower molar of the Indian Elephant (_Elephas indicus_). _d_, Dentine; _e_, enamel; _c_, cement. (From Owen.)]

In the well-known Indian or Asiatic Elephant (_E. indicus_) the average number of plates of the six successive molar teeth is expressed by the “ridge-formula,” 4, 8, 12, 12, 16, 24. The plates are compressed from before backwards, the anterior and posterior surfaces (as seen in the worn grinding face of the tooth, Fig. 181) being nearly parallel. Ears of moderate size. Upper margin of the end of the proboscis developed into a distinct finger-like process, much longer than the lower margin. Five nails on the fore feet, and four (occasionally five) on the hind feet.

[Illustration: FIG. 182.—Grinding surface of a partially worn right upper molar of the African Elephant (_Elephas africanus_). Letters as in the preceding figure. The left side of the figure is the front of the tooth, and the lower side the outer border. (From Owen.)]

This species inhabits in a wild state the forest lands of India, Burma, the Malay Peninsula, Cochin China, Ceylon, and Sumatra. The elephants from the last-named islands, presenting some variations from those of the mainland, have been separated under the name of _E. sumatranus_, but the distinction has not been satisfactorily established. The appearance of the Asiatic Elephant is familiar to all. Though rarely breeding in captivity, it has been domesticated from the most remote antiquity, and is still extensively used in the East as a beast of burden. In the wild state it is gregarious, associating in herds of ten, twenty, or more individuals, and though it may, under certain circumstances, become dangerous, it is generally inoffensive and even timid, fond of shade and solitude and the neighbourhood of water. The height of the male at the shoulder when full grown is usually from 8 to 10 feet, but occasionally as much as 11. The female is somewhat smaller.

[Illustration: FIG. 183.—African Elephant (_Elephas africanus_). From a young specimen in the London Zoological Gardens.]

In the African Elephant (_E. africanus_) the molars (Fig. 182) are of coarse construction, with fewer and larger plates and thicker enamel. Ridge-formula: 3, 6, 7, 7, 8, 10. The plates not flattened, but thicker in the middle than at the edges, so that their worn grinding surfaces are lozenge-shaped. Ears very large. The upper and lower margins of the end of the trunk forming two nearly equal prehensile lips. But three hoofs on the hind foot. This species now inhabits the wooded districts of the whole of Africa south of the Sahara, except where it has been driven away by human settlements. Fossil remains of Pleistocene age, undistinguishable specifically, have been found in Algeria, Spain, and Sicily. It was trained for war and show by the ancient Carthaginians and Romans, and recent experience of the species in captivity in England shows that it is as intelligent as its Asiatic relative, if not more so, while surpassing it in courage, activity, and obstinacy. Nevertheless, in modern times, no people in Africa have been sufficiently civilised or enterprising to care to train it for domestic purposes. It is hunted chiefly for the sake of the ivory of its immense tusks, of which it yields the principal source of supply to the European market, and the desire to obtain which is rapidly leading to the extermination of the species. In size the male African elephant often surpasses that of Asia, but the female is usually smaller. The circumference of the fore foot is half the height at the shoulder, a circumstance which enables the hunters to judge from the footprints the exact size of the animals of which they are in pursuit. The African Elephant also differs from its Indian congener in having tusks in both sexes, whereas in the latter the male only is so armed. Moreover, the eye is relatively larger, the forehead more convex, and the colour somewhat darker. Whereas the Indian Elephant frequents the depths of forests and seldom leaves their shade during the daytime, the following account by Sir Samuel Baker indicates different habits in the African species. This traveller observes: “In Africa, the country being generally more open than in Ceylon, the Elephant remains throughout the day either beneath a solitary tree or exposed to the sun in the vast prairies, where the thick grass attains a height of from nine to twelve feet. The general food of the African Elephant consists of the foliage of trees, especially mimosas. Many of the mimosas are flat-headed, about thirty feet high, and the richer portion of the foliage confined to the crown. Thus the Elephant, not being able to reach to so great a height, must overturn the tree to obtain the coveted food. The destruction caused by a herd of Elephants in a mimosa forest is extraordinary, and I have seen trees uprooted of so large a size that I am convinced no single elephant could have overturned them. I have measured trees four feet six inches in circumference and about thirty feet high uprooted by elephants. The natives have assured me that the elephants mutually assist each other, and that several engage together in the work of overturning a large tree.”

[Illustration: FIG. 184.—Restored skeleton of the Mammoth (_Elephas primigenius_). From Tilesius in _Mém. Acad. Imp. Sc. St. Pétersbourg_, vol. v. (1815). _s_, Scapula; _h_, humerus; _r_, radius; _u_, ulna; _c_, carpus; _rs_, ischium; _f_, femur; _t_, tibia; _fi_, fibula; _ta_, tarsus.]

_Extinct Species of Elephant._—Abundant remains of Elephants are found embedded in alluvial gravels, or secreted in the recesses of caves, into which they have been washed by streams and floods, or dragged as food by Hyænas and other carnivorous inhabitants of these subterranean dens. Such remains belonging to the Pleistocene and Pliocene periods have been found in many parts of Europe, including the British Isles, in North Africa, throughout the North American continent from Alaska to Mexico, and extensively distributed in Asia, where the deposits of the sub-Himalayan Siwalik Hills, and equivalent deposits in the Punjab, Perim Island,[280] and Burma, belonging to the earliest Pliocene, are rich in the remains of Elephants of varied form. These species are chiefly known and characterised at present by the skulls and teeth; some of the latter resemble the existing Indian and some the African type, but the majority are between the two, and make the distinction between the two existing species as of generic importance quite impracticable. Others again approach so closely in the breadth and coarseness of the ridges and paucity of cement to _Mastodon_ as to have been placed by some zoologists in that genus. These form the subgenus called _Stegodon_ by Falconer, and may be regarded as a distinct group of the genus.

Among the best known extinct Elephants is _E. primigenius_, the Mammoth,[281] very closely resembling the existing Indian species, and one of the most recently extinct and extensively distributed of all the fossil forms. Probably no animal which has not survived to the historic period has left such abundant and well-preserved evidence of its former existence. The discovery of immense numbers, not only, as in the case of most extinct creatures, in the form of fragmentary bones and teeth, but often as more or less nearly entire carcases, or “mummies,” as they may be called, with the flesh, skin, and hair _in situ_, in the frozen soil of the tundras of Northern Siberia, has for a long time given great interest to the species, and been the cause of many legendary stories among the natives of the lands in which they occur. Among these one of the most prevailing is that the Mammoth was, or still is, an animal which passes its life habitually in burrows below the surface of the ground, and immediately dies if by any chance it comes into the upper air.

Of the whole group the Mammoth is in many respects, as in the size and form of the tusks, and especially the characters of the molar teeth, the farthest removed from the primitive Mastodon-like type, while its nearest surviving relative, _E. indicus_, has retained the slightly more generalised characters of the Mammoth’s contemporaries of more southern climes, _E. columbi_ of America, and _E. armeniacus_ of the Old World, if, indeed, it can be specifically distinguished from them.

The tusks or upper incisor teeth were doubtless present in both sexes, but probably of smaller size in the female. In the adult males they often attained the length of from 9 to 10 feet measured along the outer curve. Upon leaving the head they were directed at first downwards and outwards, then upwards and finally inwards at the tips, and generally with a tendency to a spiral form not seen in other species of Elephant. Different specimens, however, present great variations in curve, from nearly straight to an almost complete circle.

It is chiefly by the characters of the molar teeth that the various extinct modifications of the Elephant type are distinguished. Those of the Mammoth (Fig. 185) differ from the corresponding organs of allied species in the great breadth of the crown as compared with the length, the narrowness and close approximation of the ridges, the thinness of the enamel and its straightness, parallelism, and absence of “crimping,” as seen on the worn surface, or in a horizontal section of the tooth. Dr. Falconer gave the prevailing “ridge-formula” as 4, 8, 12, 12, 16, 24. Dr. Leith Adams, working from more abundant materials, has shown, however, that the number of ridges of each tooth, especially those at the posterior end of the series, is subject to very great individual variation, ranging in each tooth of the series within the following limits: 3 to 4, 6 to 9, 9 to 12, 9 to 15, 14 to 16, 18 to 27, excluding the small plates called talons at each end of the tooth. Besides these variations in the number of ridges or plates of which each tooth is composed, the thickness of the enamel varies so much as to have given rise to a distinction between a “thick-plated” and a “thin-plated” variety—the latter being most prevalent among the specimens from the Arctic regions, and most distinctively characteristic of the species. From the specimens with thick enamel plates the transition to the other species or varieties mentioned above, including _E. indicus_, is almost imperceptible.

[Illustration: FIG. 185.—Grinding surface of upper molar of the Mammoth (_Elephas primigenius_). _c_, Cement; _d_, dentine; _e_, enamel. (From Owen.)]

The bones of the skeleton generally more resemble those of the Indian Elephant than of any other known species, but the skull differs in the narrower summit, narrower temporal fossæ, and more prolonged incisive sheaths required to support the roots of the enormous tusks. Among the external characters by which the Mammoth was distinguished from either of the existing species of Elephant was the dense clothing, not only of long coarse outer hair, but also of close woolly under hair, of a reddish-brown colour, evidently in adaptation to the colder climate which it inhabited. This character, for a knowledge of which we are indebted to the well-preserved remains found in Northern Siberia, is also represented in the rude but graphic drawings of prehistoric age found in caverns in the south of France.[282] In size different individuals varied considerably, but the average height does not appear to have exceeded that of either of the existing species of Elephant.

The geographical range of the Mammoth was very extensive. There is scarcely a county in England in which some of its remains have not been found either in alluvial deposits of gravel or in caverns, and numbers of its teeth are from time to time dredged up from the bottom of the sea by the fishermen who ply their trade in the German Ocean, having been washed out of the water-worn cliffs of the eastern counties of England. In Scotland and Ireland its remains are less abundant, but they have been found in vast numbers at various localities throughout the greater part of Central Europe (as far south as Santander in Spain and Rome), Northern Asia, and the northern part of the American continent, though the exact distribution of the Mammoth in the New World is still a question of debate. It has not hitherto been met with in any part of Scandinavia or Finland.

In point of time, the Mammoth belongs exclusively to the Pleistocene epoch, and it was undoubtedly contemporaneous with man in France, and probably elsewhere. There is evidence to show that it existed in Britain before, during, and after the glacial period.

As before indicated, it is in the northern part of Siberia that its remains have been found in the greatest abundance, and in quite exceptional conditions of preservation. For a very long period there has been from that region a regular export of Mammoth ivory in a state fit for commercial purposes, both eastward to China and westward to Europe. In the middle of the tenth century an active trade was carried on at Khiva in fossil ivory, which was fashioned into combs, vases, and other objects, as related by Abu’l Kásim, an Arab writer of that period. Middendorff reckoned that the number of tusks which have yearly come into the market during the last two centuries has been at least a hundred pairs, and Nordenskiöld, from personal observation, considers this calculation as probably rather too low than too high. They are found at all suitable places along the whole line of the shore between the mouth of the Obi and Behring Straits, and the farther north the more numerous do they become, the islands of New Siberia being now one of the most favourite collecting localities. The soil of Bear Island and of Liachoff Islands is said to consist only of sand and ice with such quantities of Mammoth bones as almost to compose its chief substance. The remains are not only found around the mouths of the great rivers, as would be the case if the carcases had been washed down from more southern localities in the interior of the continent, but are imbedded in the frozen soil in such circumstances as to indicate that the animals had lived not far from the localities in which they are now found, and they are exposed either by the melting of the ice in unusually warm summers or by the washing away of the sea cliffs or river banks by storms or floods. In this way the bodies of more or less nearly perfect animals, often standing in the erect position, with the soft parts and hairy covering entire, have been brought to light.

References to the principal recorded discoveries of this kind, and to the numerous speculations to which they have given rise, both among ignorant peasants and learned academicians, will be found in Nordenskiöld’s _Voyage of the Vega_ (English translation, vol. i. 1881, p. 398 _sq._) and a series of papers in the _Geological Magazine_ for 1880 and 1881, by H. H. Howorth, as well as in a separate work on the Mammoth by the same writer. For the geographical distribution and anatomical characters, see Falconer’s _Palæontological Memoirs_, vol. ii. 1868; Boyd Dawkins, “_Elephas primigenius_, its Range in Space and Time,” _Quart. Journ. Geol. Soc._ xxxv. p. 138 (1879); and Leith Adams, “Monograph of British Fossil Elephants,” part ii., _Palæontographical Society_ (1879).

_E. antiquus_, of the European Pleistocene, has a lower ridge-formula than in the Mammoth, the molars being narrower, and approximating to those of the African Elephant in structure. Small allied forms occur in the rock-fissures and caverns of Malta, and have been described as _E. mnaidriensis_ and _E. melitensis_; some of the individuals of the latter not exceeding 3 feet in height. The European _E. meridionalis_ is a southern form of somewhat earlier age, very common in the Upper Pliocene of Italy and France, and also in the so-called Forest-bed of the Norfolk coast. It attained very large dimensions, its height being estimated at upwards of 15 feet. The ridge-formula is lower than in _E. antiquus_, the molars are broad, with the worn enamel-discs generally expanded in the middle, and the enamel itself is crenulated.

Elephant remains are very abundant in the Pleistocene and Pliocene deposits of India, those from the latter beds being the oldest representatives of the genus. Of these the Pleistocene _E. namadicus_ appears closely allied to _E. antiquus_, from which it is distinguished by a bold ridge across the forehead. Among the Pliocene forms _E. hysudricus_ may be an ancestral type allied to the Indian Elephant; while _E. planifrons_ is closely related to _E. meridionalis_, although retaining the ancestral feature of developing premolars.

The Stegodont group is peculiar to the eastern parts of the Old World, and, as already observed, connects the true Elephants intimately with the Mastodons. The molars (Fig. 179, II) are characterised by the lowness of the ridges, while the intervening valleys may have but little cement, and there may be a more or less distinct longitudinal groove in the crown dividing each ridge into an inner and an outer moiety. In species like _E. insignis_ the ridge-formula is nearly the same as in _E. meridionalis_, but in _E. clifti_ some of the molars carry only six ridges, and premolars were present, so that we thus have such a complete transition to the next genus that it is very difficult to know where to draw the line between the two.

_Mastodon._[283]—Dentition: _i_ ¹⁄₁₋₀, _c_ ⁰⁄₀, _dm_ ³⁄₃, _m_ ³⁄₃. Upper incisors large, as in _Elephas_, sometimes with longitudinal bands of enamel, more or less spirally disposed. Lower incisors variable; when present comparatively small and straight, sometimes persistent, sometimes early deciduous, and in some species never present. Grinding surface of molars with transverse ridges, the summits of which are divided more or less into conical or mammillary cusps, and often with secondary or additional cusps between and clustering against the principal ridges; enamel thick; cement very scanty, never filling up the interspaces between the ridges. The third, fourth, and fifth cheek-teeth (_i.e._ the last milk-molar, and the first and second molars) having the same number of ridges,[284] which never exceeds five.

In the upper jaw the incisors, though of large size, were apparently never so much curved as in some species of Elephant, and they often have longitudinal bands of enamel, more or less spirally disposed upon their surface, which are not met with in Elephants. Lower incisors were present throughout life in some species, which have the symphysis of the lower jaw greatly elongated to support them (as in _M. angustidens_, _M. pentilici_, and _M. longirostris_). In the common North American species (_M. americanus_) the mandibular symphysis is short, but it may have a small incisor on one side. In other species no inferior tusks have been found, at all events in adult life (see figure of _M. arvernensis_).

The molar teeth increase in size from before backwards, but as many as three of these teeth may be in place in each jaw at one time. There is in many species a true vertical succession, affecting either the third, or the third and second, or (in _M. productus_) the first, second, and third of the six molariform teeth. These three are therefore reckoned as milk-molars, and their successors as premolars, while the last three, which are never changed, correspond to the true molars of those animals in which the typical dentition is fully developed. The study of the mode of succession of the teeth in the different species of Mastodons is particularly interesting, as it exhibits so many stages of the process by which the very anomalous dentition of the modern Elephants may have been derived by gradual modification from the typical heterodont and diphyodont dentition of the ordinary mammal. It also shows that the anterior molars of Elephants do not correspond to the premolars of other Ungulates, but to the milk-molars, the early loss of which in consequence of the peculiar process of horizontal forward-moving succession does not require, or allow time for, their replacement by premolars. It must be noted, however, that, in the Mastodon in some respects the least specialised in tooth-structure, the _M. americanus_ of North America, no vertical succession of the molars has yet been observed, although vast numbers of specimens have been examined.

[Illustration: FIG. 186.—Restoration of the skeleton of _Mastodon arvernensis_, from the Pliocene of Europe, (After Sismonda.)]

The Mastodons have fewer ridges on their molar teeth than the Elephants; the ridges are also less elevated, wider apart, have a thicker enamel-covering, and scarcely any cement filling up the space between them. Sometimes (as in _M. americanus_) the ridges are simple transverse wedge-shaped elevations, with straight or concave edges. In other species the summits of the ridges are more or less subdivided into conical cusps, and may have accessory cusps clustering around them (as in _M. americanus_, see Fig. 187). When the apices of these are worn by mastication, their surfaces present circles of dentine, surrounded by a border of enamel, and as the attrition proceeds different patterns are produced by the union of the bases of the cusps, a trilobed or trefoil form being characteristic of some species (Fig. 188).

[Illustration: FIG. 187.—Oblique side and crown view of the last upper molar of _Mastodon arvernensis_. (From Owens.)]

As already mentioned, certain of the molariform teeth of the middle of the series in Mastodons have the same number of principal ridges, those in front of them having fewer and those behind a greater number. These teeth were distinguished as “intermediate” molars by Dr. Falconer, and are three in number, namely the last milk-molar and the first and second true molars (or the third, fourth, and fifth of the whole series). The number of ridges on these intermediate molars is nearly always three or four, and the tooth in front has usually one fewer and that behind one more, so that the ridge-formula of most Mastodons can be reduced either to 1, 2, 3, 3, 3, 4, or 2, 3, 4, 4, 4, 5. The former characterises the section called _Trilophodon_ (of which an intermediate molar is shown in Fig. 188), and the latter that called _Tetralophodon_ by Dr. Falconer. These divisions are very useful, as under one or the other all the present known species of Mastodon can be ranged, but observations upon a larger number of individuals have shown that the number of ridges upon the teeth is not quite so constant as implied by the formulæ given above. Their exact enumeration is even difficult in many cases, as “talons” or small accessory ridges at the hinder end of the teeth occur in various stages of development, until they take on the character of true ridges. Transitional conditions have also been shown, at least in some of the teeth, between the trilophodont and the tetralophodont forms, and again between the latter and what has been called a “pentalophodont” type, which leads on towards the condition of dental structure characteristic of the true Elephants.

[Illustration: FIG. 188.—Grinding surface of the partially worn last left lower milk-molar of _Mastodon angustidens_, from the Upper Miocene of India. The lower side of the figure is the outer border of the tooth.]

The range of the genus _Mastodon_ in time was from the middle of the Miocene period to the end of the Pliocene in the Old World, when it became extinct; but in America several species—especially the one best known, owing to the abundance of its remains, which has been variously called _M. americanus_, _M. ohioticus_, and _M. giganteus_—survived to a late Pleistocene period.

The range in space will be best indicated by the following list of some of the better known species. (1) Trilophodont series—_M. angustidens_,[285] _borsoni_, _pentelici_, _turiensis_, from Europe; _M. falconeri_ and _pandionis_, from India; _M. americanus_, _obscurus_, and _productus_, North America; and _M. cordillerum_ and _humboldti_, South America. (2) Tetralophodont series—_M. arvernensis_, _M. longirostris_, from Europe; _M. latidens_, _sivalensis_, and _perimensis_, from India; _M. mirificus_, from North America. _Mastodon arvernensis_ and _M. longirostris_, together with a trilophodont species, occur in the crag-deposits of Norfolk and Suffolk.

_Family_ DINOTHERIIDÆ.

An extinct family distinguished from the _Elephantidæ_ by the whole series of permanent cheek-teeth being in use at the same time.

[Illustration: FIG. 189.—Skull of _Dinotherium giganteum_, from the Lower Pliocene of Eppelsheim, Hessen-Darmstadt. (After Kaup.) _p_, 3, 4, premolars; 1, 2, 3, molars.]

_Dinotherium._[286]—Dentition of adult: _i_ ⁰⁄₁, _c_ ⁰⁄₀, _p_ ²⁄₂, _m_ ³⁄₃ = 22; all present at the same time, there being no horizontal succession, but the premolars replacing milk-teeth in the ordinary manner. The presence or absence of upper incisors has not yet been clearly ascertained. Lower incisors large, conical, descending, and slightly curved backwards, implanted in a greatly thickened and deflected beak or prolongation of the symphysis. In section they do not show the decussating striæ characteristic of Mastodons and Elephants. Crowns of molars carrying strong transverse, crenulated ridges, with deep valleys between, much resembling the lower ones of the Tapirs. Ridge-formula of the permanent molar series: 2, 2, 3, 2, 2. The three ridges of the first true molar are constant in both upper and lower jaws, although it is quite an anomalous character among Proboscideans for this molar to have more ridges than those which come behind it. The last milk-molar has also three ridges, the penultimate but two. The cranium is much depressed, with comparatively little development of air-cells. The remainder of the skeleton is imperfectly known, but apparently agrees in its general character with that of the other Proboscideans.

Remains of _Dinotherium giganteum_, an animal of elephantine proportions, strikingly characterised by the pair of huge tusks descending nearly vertically from the front of the lower jaw, were first discovered at Eppelsheim, near Darmstadt, and described by Kaup. They have since been met with in various Lower Pliocene and higher Miocene formations in the south of Germany, France, Greece, and Asia Minor. Closely allied forms also occur in the Lower Pliocene and Upper Miocene of India, but none are known from America.

_Suborder_ AMBLYPODA.

_Uintatherium._[287]—Among the most remarkable of the comparatively recent discoveries in the higher Eocene formations of the western states of North America has been one of a group of animals of huge size, approaching that of the largest existing Elephants, presenting a combination of characters quite unlike those known among other recent or extinct creatures, and of which there were evidently many species living contemporaneously, but all of which became extinct before the close of the Eocene period. To form some idea of their appearance, we must imagine animals very elephantine in general proportions and in the structure of their limbs. The feet had five short toes. The tail, as in the Elephants, was long and slender, but the neck, though still short, was not so much abbreviated as in the Proboscideans, and there is no evidence that these animals possessed a trunk. The head differed greatly from that of the Elephants, being long and narrow, more like that of a Rhinoceros, and, as in that animal, was elevated behind into a great occipital crest, and it had developed upon its upper surface three pairs of conspicuous, laterally diverging protuberances—one pair in the parietal region, one on the maxillaries in front of the orbits, and one (much smaller) near the fore part of the elongated nasal bones. Whether these were merely covered by bosses of callous skin, as the rounded form and ruggedness of their extremities would indicate, or whether they formed the bases of attachment for horns of still greater extent, like those of the Rhinoceros or of the Cavicorn Ruminants, can only be a matter of conjecture. There were no upper incisors, but usually three on each side below, of comparatively small size, as was also the lower canine. A huge, compressed, curved, sharp-pointed canine tusk, very similar in form and position to that of the Musk-Deer, descended from each side of the upper jaw. These were present in both sexes, but very much smaller in the female, as was also the flange-like process of the lower jaw by which they were guarded. Behind these, and at some distance from them, were on each side above and below six cheek-teeth, of comparatively small size, placed in continuous series, each with a pair of oblique ridges conjoined internally and diverging externally in a V-like manner, and provided with a stout basal cingulum. The normal dental formula was therefore _i_ ⁰⁄₃, _c_ ¹⁄₁, _p_ ³⁄₃, _m_ ³⁄₃ = 34; and the dentition had thus already attained a remarkable degree of specialisation, although the brain was smaller and more rudimentary in characters than in almost any other known mammal. In its comparative length and the absence of a third trochanter the femur of these animals resembles that of the Proboscidea. The first discovered evidences of the existence of animals of this group were described by Leidy in 1872, under the name of _Uintatherium_ (from the Uinta mountains, near which they were found). Subsequently the names _Dinoceras_, _Tinoceras_, _Loxolophodon_, etc., have been applied to various members of the group, but the characters by which they are distinguished do not seem of sufficient importance to allow of their separation from the type genus _Uintatherium_.[288]

[Illustration: FIG. 190.—Skeleton of _Uintatherium mirabile_. ¹⁄₃₀ natural size. (From Marsh, _Am. Journ. Sci._ vol. xii. p. 2.)]

_Coryphodon._[289]—Another interesting form referred to this suborder is _Coryphodon_, which appears to connect the _Uintatheriidæ_ with the most primitive Perissodactyla. It was first described by Owen in 1846 from a fragment of a jaw from the London Clay. Other remains were afterwards discovered in France, and lately in great abundance, indicating many species from the size of a Tapir to that of a Rhinoceros, in the Lower and Middle Eocenes of New Mexico and Wyoming in the United States. _Coryphodon_ had forty-four teeth; the canines of both jaws were large and sharp pointed, and the molars had strongly pronounced oblique ridges. The general proportions were those of a Bear, but the tail was of moderate length, and the feet short and wide. The femur had a third trochanter; and the cranium was devoid of protuberances. The genus should be regarded as the type of a distinct family _Coryphodontidæ_.

[Illustration: FIG. 191.—Palatal aspect of the cranium of _Coryphodon hamatus_, from the Wasatch Eocene of New Mexico. ²⁄₉ natural size. (After Cope.)]

_Suborder_ CONDYLARTHRA.

The term Condylarthra has been proposed by Professor Cope for a number of generalised and mostly comparatively small Ungulates, which were probably allied both to the Perissodactyla and Artiodactyla, but present characters separating them from those divisions as commonly defined. In the structure of the carpus and tarsus these forms (which are chiefly known to us from the Eocene of the United States) come nearer to the Hyracoidea than to any other existing type. As a rule they have the full dental formula; the molars are brachydont, generally bunodont, and in many instances also tritubercular; while the premolars are always simpler than the molars.

The humerus is quite peculiar among Ungulates in having an entepicondylar foramen; the femur has a third trochanter; and the form and relations of the astragalus are similar to those obtaining in the Carnivora. The feet are usually furnished with five functional digits, of which the ungual phalanges are pointed. In many respects the skeleton of these remarkably generalised Ungulates approximates so decidedly to a Carnivorous type as to have led palæontologists to conclude that the Ungulata and Carnivora are branches of an original common stock.

In this work space only permits of allusion to a few of the more important types of this group. _Periptychus_, which occurs in the lowest Eocene of New Mexico, is a bunodont type readily distinguished by the vertical flutings of the premolars, and the small size of the incisors and canines. It has been suggested that this genus is closely related to the stock of the bunodont Artiodactyla. Of greater interest is the genus _Phenacodus_, which is regarded as the lowest factor in the series from which the modern Horse has been evolved, where it holds the position immediately below _Hyracotherium_ or, _Systemodon_ (see p. 374). One of the species was about the size of a Bull-dog, while another might be compared to a small Leopard. The structure of the cheek-teeth is such as might readily be modified into that obtaining in _Hyracotherium_; all the feet had five fully developed digits, and the tail was long. _Meniscotherium_ and _Hyracodontotherium_ are more specialised forms of somewhat later age, with a lophodont dentition: the latter genus being European.

_Suborder_ TOXODONTIA.

In addition to the _Macraucheniidæ_ and certain other forms noticed under the head of the Perissodactyla, the Tertiaries of South America have yielded some very remarkable forms of mammalian life, the nature and affinities of which have greatly puzzled all zoologists who have attempted to unravel them.

_Nesodon_ and _Toxodon_.—Among these _Nesodon_, from Patagonia, has the full typical Eutherian number of teeth; the crowns of the incisors being short, and the molars having a complex rhinocerotic type of structure somewhat intermediate between _Homalodontotherium_ (p. 412) and the following genus _Toxodon_. The typical species of _Nesodon_ was about as large as a Sheep, but nothing more is known of it than the teeth and portions of the skull.

_Toxodon_ is an animal about the size of a Hippopotamus; it was first discovered by Darwin, and many specimens have since been found in Pleistocene deposits near Buenos Ayres, and described by Owen, Gervais, and Burmeister. The teeth consist of large incisors, very small lower canines, and strongly curved molars, all with persistent roots, the formula being apparently _i_ ²⁄₃, _c_ ⁰⁄₁, _p_ ⁴⁄₃, _m_ ³⁄₃ = 38. The cranial characters exhibit a combination of those found in both Perissodactyles and Artiodactyles, but the form of the hinder part of the palate and the absence of an alisphenoid canal belong to the latter; and the tympanic, firmly fixed in between the squamosal and the exoccipital, ankylosed to both, and forming the floor of a long upward-directed meatus auditorius, is so exactly like that of the Suina that it is difficult to believe it does not indicate some real affinity to that group. These characters seem to outweigh in importance those by which some zoologists have linked _Toxodon_ to the Perissodactyla, and the absence of the third trochanter and the articulation of the fibula with the calcaneum tell in the same direction. According to the recent observations of Ameghino the hind feet were certainly tridactylous, and the front feet probably so. The earlier allied genera _Protoxodon_ and _Adinotherium_ are definitely known to have tridactylous front and hind feet, which conform to the Perissodactylate type, the bones of the proximal and distal rows of the carpus interlocking. _Acrotherium_, which has similar feet, differs from all other Ungulates, and indeed from all Eutherians except some individuals of the existing carnivorous genus _Otocyon_, in having eight cheek-teeth, five of which have been reckoned as premolars.

[Illustration: FIG. 192.—Cranium and Lower Jaw of _Typotherium cristatum_. ¹⁄₃ natural size. From Gervais.]

_Typotherium._—_Typotherium_ (Fig. 192), also called _Mesotherium_, from the same locality as _Toxodon_, was an animal rather larger than a Capybara, and of much the same general appearance. Its skeleton is completely known, and shows a singular combination of characters, resembling _Toxodon_ or a generalised Ungulate on the one hand, and the Rodents, especially the _Leporidæ_, on the other. In the presence of clavicles it differs from all known Ungulates, and in having two pairs of lower incisors from all Rodents. The teeth are _i_ ¹⁄₂, _c_ ⁰⁄₀, _p_ ²⁄₁, _m_ ³⁄₃ = 24.

From the Tertiaries of various parts of South America a number of forms more or less closely allied to _Toxodon_ and _Typotherium_ have been recently described, but as many of them are very imperfectly known, and there is much doubt as to their generic position, it will be unnecessary to refer to them further.

It will thus be seen that, although our knowledge of many of these forms is still very limited, we may trace among them a curious chain of affinities, which would seem to unite the Ungulates on the one hand with the Rodents on the other; but further materials are required before we can establish with certainty so important a relationship, one which, if true, would alter materially some of the prevailing views upon the classification of mammals.

_Group_ TILLODONTIA.

[Illustration: FIG. 193.—Skull of _Tillotherium fodiens_. ⅙ natural size. From Marsh.]

Here may be noticed a remarkable group of animals, called by Marsh, Tillodontia, the remains of which are found abundantly in the Lower and Middle Eocene beds of North America. They seem to combine the characters of the Ungulata, Rodentia, and Carnivora. In the genus _Tillotherium_ of Marsh (probably identical with the previously described _Anchippodus_ of Leidy) the skull (Fig. 193) resembled that of the Bears, but the molar teeth were of the Ungulate type, while the large incisors were very similar to those of the Rodents. The dental formula is _i_ ²⁄₂, _c_ ¹⁄₁, _p_ ³⁄₄, _m_ ³⁄₃. The first pair of incisors was very small; the upper molars were tritubercular, while the lower ones had crescentoid ridges as in _Palæotherium_. The skeleton resembled that of the Carnivores, but the scaphoid and lunar bones were distinct, and there was a third trochanter on the femur. The feet were plantigrade, and each had five digits, all with long pointed claws. In the allied genus _Stylinodon_ all the teeth were rootless. Some forms were as large as a Tapir.

These, with other more or less closely allied animals, such as _Calamodon_ and _Psittacotherium_, constituting a group called Tæniodonta, are included by Cope in his large order Bunotheria, to which also the existing Insectivora are referred. The dentition of some of these forms makes a remarkable approximation towards a Rodent type, while it has been suggested that there are also signs of remote Edentate affinities. The constantly increasing knowledge of these annectant forms adds to the difficulty so often referred to in this work of establishing anything like a definite classification of the heterodont mammals. An incisor tooth from the Swiss Eocene has recently been referred to _Calamodon_.

_Bibliography of Ungulata._—In addition to the works and memoirs mentioned under the different sections of the order, the following may be referred to:—W. Kowalevsky, “Monographie des genus Anthracotherium,” _Palæontographica_ 1873; Id. “Sur l’Anchitherium aurelianense et sur l’histoire paléontologique des Chevaux,” _Mém. de l’Acad. Imp. des Sciences de St. Pétersbourg_, 1873; Id. “On the Osteology of the Hyopotamidæ,” _Philosophical Transactions_, 1873; L. Rütimeyer, “Versuch einer natürlichen Geschichte des Rindes.” etc., _Neue Denks. der allgem. Schweiz. Gesellsch. für Naturwissenschaften_, 1867; Id. “Die Rinder der Tertiär-Epoche,” _Abhand. der Schweiz. Paläont. Gesellsch._ 1877 and 1878; Id. “Beiträge zu einer Natürliche Geschichte der Hirsche,” _ibid._ 1880-1881; C. J. Forsyth-Major, “Beiträge zur Geschichte der Fossilen Pferde,” _ibid._ 1880; M. Schlosser, “Beiträge zur Kenntniss der Stammesgeschichte der Hufthiere und Versuch einer Systematik der Paar- und Unpaarhufer,” _Morph. Jahrb._ 1886; E. D. Cope, “The Perissodactyla,” _Amer. Natural._ 1887; M. Pavlow, “Études sur l’histoire paléontologique des Ongulés,” _Bull. Soc. Imp. Naturalistes Moscow_, 1887-1890. W. B. Scott and H. F. Osborn, “The Mammalia of the Uinta Formation,” _Trans. Amer. Phil. Soc._ vol. xvi. (1889).