CHAPTER XII

THE ORDER INSECTIVORA

[Illustration: FIG. 280.—Right lateral aspect of the anterior portion of the cranium of _Erinaceus collaris_. Enlarged. (From Dobson, _Proc. Zool. Soc._ 1881, p. 403.)]

The Insectivora comprise a number of comparatively small mammals, generally of terrestrial, although rarely of arboreal or aquatic habits, and presenting the following common features. They are unguiculate, and have plantigrade or subplantigrade, and generally pentadactylate feet, in which the pollex and hallux are not opposable to the other digits. They are diphyodont and heterodont, and the teeth are rooted. The molars are studded with sharp cusps, the crowns of the upper molars being either quadrangular or triangular; there are never less than two incisors in either side of the mandible; and in many cases the incisors, canines, and anterior premolars are not clearly differentiated from one another (Fig. 280); the canines being usually weak. Clavicles are present, except in _Potamogale_. The body is clothed with fur or protected by an armature of spines; the testes are inguinal or placed near the kidneys, and are not received into a scrotum; the penis is pendent or suspended from the wall of the abdomen; the uterus is two-horned and with or without a distinct corpus uteri; the placenta is discoidal and deciduate; and the smooth cerebral hemispheres do not extend backwards over the cerebellum (Fig. 281). The projection of the muzzle far beyond the extremity of the lower jaw is a very general feature. The humerus generally has an entepicondylar foramen. Certain forms, such as _Talpa_ and _Galeopithecus_, are unique among mammals in having ossified intercentra in the dorso-lumbar region of the vertebral column.

Representatives of this order are found throughout the temperate and tropical parts of both hemispheres (except South America and Australia), and exhibit much variety both in organisation and in habits. With the exception of the _Tupaiidæ_, all are nocturnal; the greater number are cursorial, but some (_Talpa_, _Chrysochloris_, _Oryzorictes_) are fossorial; some (_Potamogale_, _Nectogale_, _Myogale_) are natatorial, and a few (_Tupaiidæ_) arboreal; while the species of the aberrant genus _Galeopithecus_ glide through the air like the Flying Squirrels. To the great majority the term insectivorous is strictly applicable, _Galeopithecus_ alone being phytophagous; while _Potamogale_ is said to feed on fish, and the different species of Moles live chiefly on worms. The general organisation of the Insectivora indicates a very low type, and were it not for the specialised character of their placentation and the tendency to lose the differentiated characters of the anterior teeth they might be regarded as closely allied to the ancestral type of many of the heterodont mammals. The strongly marked distinction of the canines from the incisors and anterior premolars in the Mesozoic and most of the Tertiary mammals (excepting some of the Ungulates) points, however, very decidedly to the conclusion that the want of definition between these teeth in many of the modern Insectivora is an acquired feature. Fossil forms apparently indicate a relationship on the one hand with the Creodont Carnivora, and on the other with the Lemuroid Primates; indeed it is in some instances impossible to say whether extinct genera are really Insectivores or Lemuroids.

[Illustration: FIG. 281.—Upper surface of the brain of _Tupaia ferruginea_. (From Garrod, _Proc. Zool. Soc._ 1879, p. 304.)]

In most Insectivora the cranial cavity is of small relative size, and in none is the brain-case elevated to any considerable extent above the facial line. The facial part of the skull is generally much produced, and the premaxillary and nasal bones are well developed. The zygomatic arch is usually slender or deficient, the latter being the case in most of the species; and postorbital processes of the frontals are found only in the _Galeopithecidæ_, _Tupaiidæ_, and _Macroscelididæ_. The number of dorsal vertebræ varies from 13 in _Talpa_ to 19 in _Centetes_; that of the lumbar from 3 in _Chrysochloris_ to 6 in _Talpa_ and _Sorex_; and of the caudal from the rudimentary series of 8 in _Centetes_ to the 40 or more of _Microgale_. Not less variable are the characters of the vertebræ themselves; the spinous processes often being very long in one and short in another species of the same genus. In the _Soricidæ_ and _Myogale_ the neural arches of the cervical vertebræ are very slender. In the _Soricidæ_ and _Gymnura_ the four anterior vertebræ develop large single hypapophyses. In _Galeopithecus_ the centrum of each vertebra supports posteriorly a pair of intercentral ossifications; while in _Erinaceus_, _Myogale_, and _Talpa_ small oval ossicles are found on the inferior surfaces of the lumbar interspaces. In _Erinaceus_, owing to the thickness of the neural cord in the cervical region and its abrupt termination, the diameter of the neural canal in the cervical and first two dorsal vertebræ greatly exceeds that of any of the succeeding vertebræ. The sternum is variable, but generally narrow, bilobate in front, and divided into segments. The pectoral girdle presents some remarkable adaptive modifications, most fully expressed in _Talpa_, having relation to the use of the fore limbs in burrowing; but in the Golden Moles (_Chrysochloris_) the forearm and manus alone become specially modified for this purpose. In _Galeopithecus_ and _Macroscelides_ the bones of the forearm (radius and ulna) are distally united. The manus has generally five digits, but in _Rhynchocyon_ and in one species of _Oryzorictes_ the pollex is wanting, while in the true Moles it is extremely modified. The femur has, in most species, a prominent ridge below the greater trochanter representing a third trochanter. In _Galeopithecus_, _Tupaia_, _Centetes_, _Hemicentetes_, _Ericulus_, and _Solenodon_ the tibia and fibula are distinct, but in all the other genera more or less united together. The pes usually possesses five digits (rarely four by reduction of the hallux); and in some forms, as in the leaping species (_Macroscelides_, _Rhynchocyon_), the tarsal bones are greatly elongated. The form of the pelvis, and especially of the symphysis pubis, varies within certain limits; and these differences have been proposed by Leche as a basis for the classification of the families. Thus in the _Galeopithecidæ_, _Tupaiidæ_, and _Macroscelididæ_ there is a long symphysis; in the _Erinaceidæ_, _Centetidæ_, and _Potamogalidæ_ the symphysis is short; and in the _Soricidæ_, _Talpidæ_, and _Chrysochloridæ_ there is none.

Space does not admit of attempting a sketch of the modifications of the muscular system, which will be found fully described in Dr. Dobson’s _Monograph_, referred to in the bibliography. As to the nervous system, it has been already mentioned that the brain throughout the order presents a low type of organisation; in none of the members do the cerebral hemispheres present any trace of convolutions, nor do they extend backwards so as to cover the cerebellum, while the olfactory lobes are large and project in front, and the corpus callosum is short and thin. In the Hedgehogs (_Erinaceus_) the spinal column ends abruptly opposite the third or fourth dorsal vertebra in a slender filament, and the dorsal and lumbar nerves, given off in front of this point, are carried backwards in two compressed bundles occupying the suddenly narrowed spinal canal as far as the sacrum.

Owing to the similarity in the character of the food, the truly insectivorous species, forming more than nine-tenths of the order, present little variety in the structure of their digestive organs. Except in _Galeopithecus_ the stomach is a simple, thin-walled sac; but in some, as in _Centetes_ and allied genera, the pyloric and œsophageal openings are very close together. The intestinal canal has much the same calibre throughout, and varies from three (in the Shrews) to twelve times (in the Hedgehogs) the length of the head and body. In the arboreal genera, _Galeopithecus_ and _Tupaia_, as well as in the _Macroscelididæ_, all of which probably feed in part on vegetable substances, most of the species possess a cæcum. The liver is deeply divided into lobes, the right and left lateral being cut off by deep fissures; and both the caudate and Spigelian lobes being generally well developed. The gall-bladder, which is usually large and globular, is placed on the middle of the posterior surface of the right central lobe.

In most of the members of the order (_Soricidæ_, _Centetidæ_, _Chrysochloridæ_) the penis is capable of being more or less completely retracted within the fold of integument surrounding the anus; in some (_Galeopithecidæ_, _Talpidæ_) it is pendent in front of the anus; while in others (_Macroscelididæ_, _Erinaceidæ_, _Solenodontidæ_) it is carried forwards and suspended from the abdominal wall. In the subfamily _Centetinæ_ and _Chrysochloris_ the testes lie immediately behind the kidneys, but in others more or less within the pelvis. During the rutting season they become greatly enlarged, forming protrusions in the inguinal region. Except in _Rhynchocyon_ the uterine cornua are long and open into a short corpus uteri, which in many species (_Soricidæ_, _Talpidæ_, _Centetidæ_, _Chrysochloridæ_) is not separated from the vagina by a distinct os uteri. With the exception of _Galeopithecus_ all Insectivora appear to be multiparous, the number of young at a birth varying from two to eight in _Erinaceus_, and from twelve to twenty in _Centetes_. The position of the mammary glands and the number of the teats vary greatly. Thus in _Galeopithecus_ there are two pairs of axillary teats, and in _Solenodon_ a single post-inguinal pair; but in most species they range from the thorax to the abdomen, varying from two pairs in _Gymnura_ to twelve in _Centetes_. In _Chrysochloris_ the thoracic and inguinal teats are lodged in deep cup-shaped depressions.

Odoriferous glands exist in many species. In most Shrews these glands occur on the sides of the body at a short distance behind the axilla, and their exudation is probably protective, since few carnivorous animals will eat the dead bodies of these creatures. In both species of _Gymnura_ and in _Potamogale_ large pouches are situated on either side of the rectum and discharge their secretions by ducts, opening in the first-named genus in front of, and in the latter within the margin of the anus. In _Centetes_ the ducts of similarly situated racemose glands open by pores at the bottom of deep pits placed at either side of the anus.

The integument is thin, but in many species is lined by a muscular coat, which is probably more developed in the Hedgehogs (_Erinaceidæ_) than in any other mammal. In this family and the _Centetidæ_ most of the species are protected by spines implanted in the panniculus carnosus muscle, and more or less replacing the fur of the upper surface of the body.

The order is usually divided into two suborders, but the very aberrant genus which constitutes the first might well be raised to ordinal rank. It has little in common with the true Insectivora, but as it certainly belongs to no other of the recognised mammalian orders it is retained among them chiefly to avoid the inconvenience of increasing the number of ordinal divisions for the sake of a single isolated form.

_Suborder_ DERMOPTERA.

Upper and lower incisors compressed, multicuspidate, the lower deeply pectinated; fore and hind limbs connected by a broad integumentary expansion forming a parachute.

_Family_ GALEOPITHECIDÆ.

In addition to the characters given under the head of the suborder it may be mentioned that the orbit is nearly surrounded by bone, the zygomatic arches are well developed, the tympanic forms a bulla, the ulna is distally united with the radius, the tibia and fibula are distinct, the pubic symphysis is long, the penis is pendent, the testes are received into inguinal pouches, the mammæ are axillary, the uterus is two-horned, and there is a large cæcum.

_Galeopithecus._[530]—Dentition: _i_ ²⁄₃, _c_ ¹⁄₁, _p_ ²⁄₂, _m_ ³⁄₃; total 34. Second upper incisor and canine with two roots. Two species—_G. volans_ and _G. philippinensis_. The former, which is distinguished from the latter by the form of the upper incisors, has a total length of nearly 2 feet. The long and slender limbs are connected by a broad integumentary expansion extending outwards from the sides of the neck and body, and forming also a web between the fingers and toes as far as the base of the claws (Fig. 282); the hind limbs are further connected by a similar expansion passing outwards along the back of the feet to the base of the claws, and, inwardly, involving the long tail to the tip, forming a true interfemoral membrane, as in the Bats.

The two species of Flying Lemurs, as the representatives of this genus are commonly but erroneously called, live in the forests of the Malay Peninsula, Sumatra, Borneo, and the Philippine Islands, where they feed chiefly on the leaves and fruits of trees. Their habits are nocturnal, and during the daytime they cling to the trunks or limbs of trees, head downwards, in a state of repose. With the approach of night their season of activity commences, when they may be seen gliding from tree to tree supported on their cutaneous parachute, and they have been observed to traverse in this way a space of 70 yards with a descent of only about one in five.

[Illustration: FIG. 282.—Feet of _Galeopithecus philippinensis_.]

_Galeopithecus_ was referred by some of the older zoologists and anatomists to the Bats, and by others to the Lemurs, but Professor Peters’s view, that it belongs to neither of these orders, and should be considered an aberrant Insectivore, has been very generally accepted, although, as mentioned above, the association is by no means a close one. Besides differing from the Bats in the form of the anterior limbs and of the double-rooted outer incisor and canine, it also contrasts strongly with them in the presence of a large sacculated cæcum, and in the great length of the colon, which is so remarkably short in all the Chiroptera. From the Lemurs, on the other hand, the form of the brain, the characters of the teeth, the structure of the skull, and the deciduate discoidal placenta completely separate it. In a recent elaborate memoir on the myology and affinities of _Galeopithecus_ Dr. Leche[531] considers that we have in this genus an indication of the mode in which the Insectivora were modified into the Chiroptera, although it is completely off the direct line of descent. The deeply pectinated crowns of the lower incisors of _Galeopithecus_ are quite unique in the class, and the only approach to the double-rooted canine, except in _Erinaceus_ and _Talpa_, is found among the Marsupials in _Perameles_, where the root of the canine is grooved.

_Suborder_ INSECTIVORA VERA.

Upper and lower incisors conical, unicuspidate or with basal cusps only, the lower not pectinated; limbs free, formed for terrestrial progression.

The following table gives a key to the distinctive characters of the existing families:—

I. Upper molars broad, multicuspidate, with more or less well-defined W-shaped crowns.

A. Symphysis pubis long; generally a cæcum; cerebral cavity comparatively large.

_a._ Orbit encircled by bone; metatarsus moderate; arboreal. _Tupaiidæ_.

_b._ Orbit not encircled by bone; metatarsus greatly elongated; terrestrial. _Macroscelididæ._

B. Symphysis pubis short or none; no cæcum; cerebral cavity small; skull without postorbital processes.

_a._ First and second upper molars with a central fifth cusp.

_a′._ Tympanic annular, not forming a bulla. _Erinaceidæ._

_b._ No central fifth cusp to upper molars.

_a′._ Tympanic annular, not forming a bulla; no zygomatic arch. _Soricidæ._

_b′._ Tympanic forming a bulla; zygomatic arch developed. _Talpidæ._

II. Upper molars narrow, with V-shaped crowns.

_a′._ Tympanic annular, not forming a bulla; zygomatic arch imperfect.

_a″._ No clavicles. _Potamogalidæ._

_b″._ Clavicles well developed.

_a‴._ Skull constricted between the orbits; penis suspended. _Solenodontidæ._

_b‴._ Skull not constricted; penis pendent, retractile. _Centetidæ._

_b′._ Tympanic forming a bulla; zygomatic arch well developed. _Chrysochloridæ._

The second section, in which the molars are of the primitive tritubercular type, should probably be regarded as containing the most generalised representatives of the order; and it is noteworthy that the whole of them are confined to Africa, Madagascar, and the West Indies, whereas most of the first section are widely distributed over the Palæarctic and Oriental regions. None of the existing families of the second section are known in a fossil condition, although it is suggested that the extinct _Leptictidæ_ includes allied types.

_Family_ TUPAIIDÆ.

Skull with comparatively large brain-case, orbit surrounded by bone, well-developed zygomatic arch, perforated jugal, and a tympanic bulla. Upper molar broad, with cusps arranged in a W. Pubic symphysis long; radius and ulna, and tibia and fibula separate; metatarsus only slightly longer than tarsus. Usually a short cæcum. Habits arboreal and diurnal. Confined to the Oriental region.

[Illustration: FIG. 283.—The Pentailed Tree-Shrew (_Ptilocercus lowi_). From Gray, _Proc. Zool. Soc._ 1848. ½ natural size.]

_Tupaia._[532]—Dentition: _i_ ²⁄₃, _c_ ¹⁄₁, _p_ ³⁄₃, _m_ ³⁄₃; total 38. Feet naked beneath, the sole furnished with projecting pads; claws moderate, curved, and sharp; head pointed; ears rounded; tail bushy, distichous, with short hair below. The Tree-Shrews, of which there are some nine species, are found in India, Burma, the Malay Peninsula, the Nicobars, Sumatra, Java, and Borneo. The species closely resemble one another, differing chiefly in size and in the colour and length of the fur. Their general appearance is very Squirrel-like. Their food consists of insects and fruit, which they usually seek in the trees, but also occasionally on the ground. When feeding they often sit on their haunches, holding the food, after the manner of Squirrels, between their forepaws.

_Ptilocercus._[533]—Represented only by the Pentailed Tree-Shrew (_P. lowi_, Fig. 283) of Borneo, in which the tail is of extraordinary length, with the proximal two-thirds naked, and the remaining third furnished with a bilateral fringe of long hairs, from which the genus takes its name.

_Extinct Genera._—An Insectivore from the Middle Miocene of France, described as _Lantanotherium_, is said to be nearly allied to _Tupaia_. The genus _Parasorex_, from strata of similar age, has the dental formula _i_ ³⁄₃, _c_ ¹⁄₁, _p_ ⁴⁄₄, _m_ ³⁄₃, and is regarded as connecting the present with the following family.

_Family_ MACROSCELIDIDÆ.

Skull with comparatively large brain-case, strong zygomatic arch, a tympanic bulla, orbit surrounded by bone, imperforate jugal, and usually no postorbital process. Molars broad, with four cusps arranged in a W. Pubic symphysis long; proximal end of tibia and fibula united; radius and ulna united or separate; metatarsus much longer than tarsus. A large cæcum. Habits terrestrial, saltatorial, and nocturnal. The family is confined to Africa.

_Macroscelides._[534]—Dentition: _i_ ³⁄₃, _c_ ¹⁄₁, _p_ ⁴⁄₄, _m_ ²⁄₂₋₃; total 40 or 42. Distal extremity of radius and ulna united. Five digits in manus, and five or four in pes. This genus, which is taken to include _Petrodromus_, comprises ten species widely distributed throughout the African continent. All are closely related, resembling one another in general form, and even in the colour of the fur. They fall into two groups, distinguished by the presence or absence of a small third lower molar.[535] _M. tetradactylus_ (Fig. 284), the type of the genus _Petrodromus_, differs from all the other species in the absence of the hallux, and of the third lower molar. These animals are commonly known as Jumping Shrews, and, like the following genus, have the muzzle much produced.

_Rhynchocyon._[536]—Dentition: _i_ ¹⁄₃, _c_ ¹⁄₁, _p_ ⁴⁄₄, _m_ ²⁄₂; total 36. Upper incisor frequently shed in the adult. Radius and ulna distinct; hind limbs relatively shorter, and proboscis longer than in the type genus; four digits in each foot. Four closely allied species have been described from East Africa. The head and body of the type species measures about 8 inches in length; and the long tail is covered with a ringed skin, sparsely haired. Its habits are fossorial.

[Illustration: FIG. 284.—_Macroscelides tetradactylus._ × ½. (From Peters, _Reise nach Mossambique._)]

_Family_ ERINACEIDÆ.

Skull with a small brain-case; no postorbital process; slender and occasionally imperfect zygomatic arch, and an annular tympanic, which does not form a bulla. Upper molars with four principal cusps and a small central median cusp. Acromion of scapula bifid; pubic symphysis short; radius and ulna free, but tibia and fibula united proximally. No cæcum; penis carried forward and suspended from the wall of the abdomen. Habits terrestrial. Found in the Palæarctic, Ethiopian, and Oriental regions.

Subfamily =Gymnurinæ=.—Palate completely ossified; pelvis very narrow; fur without spines.

_Gymnura._[537]—Dentition: _i_ ³⁄₃, _c_ ¹⁄₁, _p_ ⁴⁄₄, _m_ ³⁄₃; total 44. This genus, if _Hylomys_ is rightly included, is represented by the two species, _G. rafflesi_ and _G. suilla_, from the Malay Peninsula and Indian Archipelago. The former has the appearance of a large Rat with a long tail and head and projecting mobile snout; the latter, which is much smaller, with a short tail and small third upper premolar, has long been known under the name of _Hylomys suillus_, and classed with the _Tupaiidæ_. Both species present a very generalised type of dentition, in this respect occupying an almost central position in the order. _G. suilla_ is represented in Mount Kina-Balu, Borneo, by a variety characterised by the presence of a dark dorsal streak. Many zoologists prefer to retain _Hylomys_ as a distinct genus.

Subfamily =Erinaceinæ=.—Palate imperfectly ossified; pelvis wide; fur with spines.

_Erinaceus._[538]—Dentition: _i_ ³⁄₂, _c_ ¹⁄₁, _p_ ³⁄₂, _m_ ³⁄₃; total 36. The first pair of upper incisors (Fig. 285) are considerably larger than the others, and are widely separated from one another in the middle line; the canine is very similar to the third incisor; and, except in _E. europæus_ (Fig. 285), each of these teeth is inserted by two distinct roots (Fig. 280, p. 610). The first lower incisor is large and proclivous. The number of vertebræ is C 7, D 15, L 6, S 3, C 11.

[Illustration: FIG. 285.—Right lateral aspect of the anterior portion of the skull of the Hedgehog (_Erinaceus europæus_). Enlarged. (From Dobson, _Proc. Zool. Soc._ 1881, p. 403.)]

The Hedgehogs comprise nearly twenty species, distributed throughout Europe, Africa, and the greater part of Asia, but not found in Madagascar, Ceylon, Burma, Siam, the Malay Peninsula, or Australia. All the species resemble one another in the armature of spines investing the upper surface and sides of the body; and all possess the power of rolling themselves up into the form of a ball, protected on all sides by the strong spines; the dorsal integument being brought downwards and inwards over the head and tail, so as to include the limbs also, by the action of special muscles. The common Hedgehog (_E. europæus_) is the most aberrant species, differing from all the rest in the peculiarly shaped and single-rooted third upper incisor and canine (Fig. 285), and in its very coarse, harsh fur. The dentition of the long-eared North Indian form, _E. collaris_ (Fig. 280), may be considered characteristic of all the other species, the only important differences being found in the variable size and position of the second upper premolar, which is very small, external, and deciduous in the Indian _E. micropus_ and _pictus_. The former species, limited to South India, is further distinguished by the absence of the jugal bone. Of the African species, _E. diadematus_, with long frontal spines, is probably the commonest; while _E. albiventris_ has been made the type of a separate genus on account of the total absence of the hallux.

The well-known European species feeds on insects, worms, slugs, mice, rats, lizards, snakes, etc., as well as on eggs, fruit, and roots. It hibernates during the winter. The young are usually produced in July or August in litters of not more than four, but there may be a second litter in October; and the period of gestation is believed not to exceed a month. The Indian, and probably also the African species, do not hibernate.

The existing _E. europæus_ dates from the Pleistocene period, and extinct species of the genus are found in the Upper and Middle Miocene of the Continent.

_Extinct Genera._—The French Lower Miocene genus, _Palæoerinaceus_, appears to be allied to _Erinaceus_, but is distinguished by the wider and completely ossified palate. In the Upper Eocene of Central France there are two genera, which appear to be most nearly allied to _Gymnura_, although connected by _Palæoerinaceus_ with _Erinaceus_. Of these _Necrogymnurus_,[539] with which _Cayluxotherium_ is apparently identical, has teeth like _Gymnura_, but an imperfectly ossified palate like _Erinaceus_; and the skull is remarkable for the peculiar rugose structure of the parietal and temporal regions. _Comphotherium_ is distinguished by the presence of a cingulum to the lower molars, like that found in _Gymnura_.

_Family_ SORICIDÆ.

Skull (Fig. 286) long and narrow, with no zygomatic arch or postorbital process, and the tympanic ring-like and not forming a bulla. Upper molars with the cusps arranged in a distinct W. No pubic symphysis. The tibia and fibula united. No cæcum. Habits usually terrestrial, rarely aquatic. Distribution extensive.

The Shrews are Rat-like or Mouse-like insectivores, with the body covered with hair, and the muzzle long and pointed. Their dentition (Fig. 286) is peculiar and characteristic. Thus the first upper incisor is large and hook-like, with a more or less developed basal cusp on the posterior border. Between this and the last premolar there are a variable number of small teeth, representing the other incisors, the canine, and the anterior premolars; although, owing to the early obliteration of the maxillo-premaxillary suture, their homology is exceedingly difficult to determine. Three molars are invariably present, of which the third is much the smallest. In the mandible there are always six teeth, but in one species of _Myosorex_ there may be a seventh. The first lower incisor is usually directed horizontally forwards; the second incisor (formerly reckoned as the canine) is the smallest tooth of the series, the fourth premolar being slightly larger.

This family, which includes considerably more than half the representatives of the order, has a distribution coextensive with the latter. Many classifications of this difficult group have been attempted, but according to the latest proposal of Dr. Dobson,[540] the genera may be divided into two subfamilies, distinguished by the apparently trivial character of the colour of the teeth.

[Illustration: FIG. 286.—Left lateral view of the cranium and mandible of _Sorex veræpacis_. In the cranium—_i_, first incisor; _c_, fourth incisor; _p_, canine; _m_, fourth premolar: in the mandible—_i_, first incisor; _c_, second incisor; _p_, fourth premolar; _m_, first molar. (From Alston, _Proc. Zool. Soc._ 1877.)]

Subfamily =Soricinæ=.—Summits of the teeth coloured red.

_Sorex._[541]—Dentition: _i_ ⁴⁄₂, _c_ ¹⁄₀, _p_ ²⁄₁, _m_ ³⁄₃; total 32. Openings of male and female generative organs separated from the anal orifice; penis cylindrical or tapering; ear well developed; tail long, covered with equal or subequal hairs.

It has been shown by Brandt that the position of the premaxillo-maxillary sutures in the type of the genus is between the fourth and fifth tooth, so that it appears that we must regard this genus as differing from all other Eutherian mammals in having four upper incisors. Dr. Dobson, in his paper quoted, classes the tooth here reckoned as the upper canine with the premolar series in all the Shrews. Habits terrestrial. Species numerous, inhabiting the Palæarctic and Nearctic regions.

Of the two species found in the British Isles the Common Shrew (_S. vulgaris_, Fig. 287) is by far the most common in England, and is about the size of the House Mouse, to which it approximates in general form. The body is clothed with close long fur, very soft and dense, and varying in colour from light reddish to dark brown above, rarely speckled or banded with white. The under surface of both the body and the tail is grayish. The basal four-fifths of all the hairs above and beneath are dark bluish-gray; the hairs of the tail are less densely set and coarser. On each side of the body, at a point about one-third of the distance between the elbow and the knee, may be found, especially in the rutting season, a gland covered by two rows of coarse hairs. This secretes a peculiar fluid, on which the odour of the animal depends; this odour being evidently protective, and rendering the creature secure against the attacks of many predaceous animals.

The geographical range of the Common Shrew is exceedingly wide, extending eastwards through Europe and Asia (north of the Himalayas) to North America.

[Illustration: FIG. 287.—The Common Shrew (_Sorex vulgaris_).]

The Lesser Shrew (_S. pygmæus_[542]) is far less common in England and Scotland, although more abundant in Ireland, where _S. vulgaris_ is unknown. It is distinguished from the latter not only by its inferior dimensions, but also by the circumstance that the third upper incisor is not longer than the fourth, and by the considerably shorter length of the forearm and manus. This species extends through Europe and Asia as far as the inland of Saghalin. Both this and the preceding species generally live in wooded districts, making their nests under the roots of trees, or in slight hollows. The great mortality noticeable among the Shrews in the early part of the autumn is probably due to insufficiency of food. The breeding season extends from the latter part of April to the beginning of August. The young, which are blind, naked, and toothless at birth, are very quickly developed. The number in a litter is usually from five to seven, but may be as many as ten.

The Alpine Shrew (_S. alpinus_), which is restricted to the Alpine region of Central Europe, is slightly larger than the common species, from which it is distinguished by the longer tail, the length of which exceeds that of the head and body, by the fur being dark on both surfaces of the body, and also by the larger size of the upper canine.

In North America _S. bendirei_ is by far the largest species of the genus; and, as in many other species of the same country, the fourth upper incisor is relatively small. In _S. hoyi_ (separated by some writers as _Microsorex_), of the same country, this tooth is rudimentary.

Other North American Shrews, which are regarded by some zoologists as generically distinct under the name of _Neosorex_, are aquatic, and thus take the place of the Old World genus _Crossopus_. These are _S. palustris_ of the Rocky Mountains and _S. hydrodromus_ of Unalaska Island, both of which resemble _Crossopus_ in having the feet provided with swimming fringes, but agree with the other species of _Sorex_ in their dentition and the character of the tail. The former species is about the size of _Crossopus fodiens_, while the latter is scarcely larger than _S. pygmæus_.

_Soriculus._[543]—Dentition: _i_ ⁴⁄₂, _c_ ¹⁄₀, _p_ ¹⁻²⁄₁, _m_ ³⁄₃; total 30, or rarely 32. Opening of male or female generative organs forming with the anal orifice a shallow cloaca. Ear and tail as in _Sorex_. First upper incisor with an internal cusp. Habits terrestrial.

This genus is the only representative in the Oriental region of the _Soricinæ_, which are otherwise confined to the Palæarctic and Nearctic regions. The Indian and Burmese species comprise _S. nigrescens_, _S. caudatus_, and _S. macrurus_.

_Notiosorex._[544]—Dentition: _i_ ³⁄₂, _c_ ¹⁄₀, _p_ ¹⁄₁, _m_ ³⁄₃; total 28. Tail moderate; first upper incisor without an inner cusp; other characters as in _Soriculus_. Habits terrestrial.

This American genus is represented by _S. crawfordi_ and _S. evotis_, which are found in Central America and Mexico, and are thus some of the most southerly representatives of the Shrews in that continent. Their external appearance is very similar to that of the Old World genus _Crocidura_.

_Blarina._[545]—Dentition: _i_ ⁴⁻³⁄₂, _c_ ¹⁄₀, _p_ ²⁄₁, _m_ ³⁄₃; total 32 or 30. Ear truncated above; tail short; otherwise as in _Soriculus_. This group of so-called Earless or Short-tailed Shrews is mainly North American, the common forms being _B. dekayi_ and _B. brevicauda_. The species vary considerably in size; and _B. mexicana_ and _micrura_ extend the range of the genus into Mexico and Guatemala. The following account of the habits of _B. brevicauda_ is taken from Dr. Merriam’s _Mammals of the Adirondack Region_: “The rigours of our northern winters seem to have no effect in diminishing its activity, for it scampers about on the snow during the severest weather, and I have known it to be out when the thermometer indicated a temperature of -20° Fahr. It makes long journeys over the snow, burrowing down whenever it comes to an elevation that denotes the presence of a log or stump, and I am inclined to believe that at this season it must feed largely upon the chrysalides and larvæ of insects that are always to be found in such places.” Dr. Merriam has made the interesting discovery that the common short-tailed North American Shrew supplements its insectivorous fare by feeding on beech-nuts, which will account for the generally very worn state of the teeth in this species.

_Crossopus._[546]—Dentition: _i_ ³⁄₂, _c_ ¹⁄₀, _p_ ²⁄₁, _m_ ³⁄₃; total 30. Opening of male or female generative organs enclosed within the same ring as the anal orifice; penis broad, with lateral processes. Ears small, not truncated. Tail long, with an inferior fringe of elongated hair; feet also fringed. Habits aquatic. The Palæarctic Water-Shrew (_C. fodiens_) is considerably larger than the Common Shrew, from which it is readily distinguished externally by its shorter and much broader muzzle, comparatively smaller eyes, and larger feet adapted for swimming,—the sides of the feet and toes being provided with comb-like fringes of stiff hairs. The tail is longer than the body, and possesses a well-developed swimming fringe of moderately long, regularly arranged hairs, which extend along the middle of the flat under surface from the end of its basal third to its extremity. The fur of the body is long and very dense, varying much in colour in different individuals, and this has given rise to descriptions of many nominal species; the prevailing shades are dark brown, almost black, above, and more or less bright ashy tinged with yellowish beneath; sometimes in the same litter there are individuals with the under surface more or less dark coloured. In the number as well as in the shape of the teeth the Water-Shrew differs from the Common Shrew: there is a premolar less on each side above; the bases of the teeth are much more prolonged posteriorly; and their cusps are much less stained brown, so that in old individuals with worn teeth they often appear altogether white. This species resembles the otter in its aquatic habits, swimming and diving with great agility. It frequents rivers and lakes, making its burrows in the overhanging banks, from which when disturbed it escapes into the water. Its food consists of insects and their larvæ, small crustaceans, and probably the fry of small fishes. It is generally distributed throughout England, is less common in Scotland, and as yet it has not been recorded in Ireland; specimens have been obtained from many parts of Europe, and also from Asia as far eastward as the Altai Mountains.

Subfamily =Crocidurinæ=.—Teeth completely white.

_Myosorex._[547]—Dentition: _i_ ³⁄₂, _c_ ¹⁄₀, _p_ ²⁄₁₋₂, _m_ ³⁄₃; total 30 or 32. Penis cylindroid and tapering; male or female generative organs opening close to anal orifice, but not forming a cloaca. Ears well developed; tail long, clothed with equal or subequal hairs. Habits terrestrial.

This genus is typically represented by _M. varius_, a very small Shrew from the Cape, which is quite unique among the whole family in having a rudimental seventh pair of lower teeth.

_Crocidura._[548]—Dentition: _i_ ³⁄₂, _c_ ¹⁄₀, _p_ ²⁻¹⁄₁, _m_ ³⁄₃; total 28 or 30. Male or female generative organs forming a short cloaca with the anal orifice. Tail long, with a mixture of long and short hairs. Other characters as in _Myosorex_. Habits terrestrial.

This Old World genus includes over seventy nominal species, which have been divided into four subgenera, _C. aranea_ and _C. suaveolens_ of Continental Europe, and _C. cœrulea_ of India, being well-known forms. The species are very variable and difficult to discriminate. _C. aranea_ has a very wide distribution, ranging from Central and Southern Europe to North Africa and Central Asia. The name Musk-Rat is popularly applied in India to _C. cœrulea_, which frequents houses at night, hunting round rooms for cockroaches and other insects, and occasionally uttering a sharp shrill cry. The strong musky odour of this animal arises from large glands situated beneath the skin of the side of the body, a short distance behind the fore limbs. This odour is so powerful and penetrating that it is popularly believed in India that if the animal runs over a corked bottle of wine or beer it will infect the fluid within. Jerdon says that certainly many bottles are met with quite undrinkable from the peculiar musky odour of their contents, but, rejecting the possibility of its passing through the glass, he attributes it to the corks having been infected previously to bottling, stating in corroboration of this view that he has never found the odour in liquors bottled in England.

_Diplomesodon._[549]—Dentition: _i_ ²⁄₂, _c_ ¹⁄₀, _p_ ¹⁄₁, _m_ ³⁄₃; total 26. Tail moderate; soles of the feet hairy. Other characters as in _Crocidura_. Habits terrestrial.

This genus is represented only by _D. pulchellus_ of the Kirghiz steppes, which is allied to the following form, although retaining the normal Shrew-like external contour.

_Anurosorex._[550]—Dentition: _i_ ²⁄₂, _c_ ¹⁄₀, _p_ ¹⁄₁, _m_ ³⁄₃; total 26. Ear very short; tail rudimental or short; soles of feet naked. Other characters as in _Diplomesodon_.

The two species of this genus are Mole-like terrestrial forms, of which the typical _A. squamipes_ occurs in Tibet, while _A. assamensis_ is found in Assam. The latter species has the longer tail. The habits of both are probably fossorial.

_Chimarrogale._[551]—Dentition: _i_ ³⁄₂, _c_ ¹⁄₀, _p_ ¹⁄₁, _m_ ³⁄₃; total 28. Penis broad, with lateral processes; male or female generative organs opening within the same integumentary ring as the anal orifice. Tail long, with an inferior fringe of elongated hairs; ears small; plantar callosities simple; toes free. Habits aquatic.

This genus includes _C. himalayica_ of the Himalaya and _C. platycephalus_ of Japan. Both have the feet fringed, and, together with the next genus, may be regarded as the eastern analogues of _Crossopus_ among the red-toothed series; their structural resemblances to the latter, if Dr. Dobson’s classification is a natural one, being probably due to adaptation for a similar mode of life.

_Nectogale._[552]—Dentition: _i_ ³⁄₂, _c_ ¹⁄₀, _p_ ¹⁄₁, _m_ ³⁄₃; total 28. External ears not forming a conch, valvular. Plantar callosities forming adhesive pads; toes webbed. Other characters as in _Chimarrogale_. Habits aquatic.

[Illustration: FIG. 288.—_Nectogale elegans._ (From Milne-Edwards, _Mammif. Tibet_.)]

The sole representative of this genus is the Tibetan Water-Shrew (_N. elegans_, Fig. 288), which differs from all other members of the family by the webbed toes and the presence of the disc-like adhesive pads on the under surface of the feet, which are believed to enable the creature to hold on to smooth rocks or stones in the beds of the streams it inhabits. This species is probably more completely aquatic in its habits than the allied _Chimarrogale_.

_Fossil Soricidæ._—Remains of existing species of _Sorex_ or _Crossopus_ occur in the Norfolk Forest bed, while an extinct species has been found in the Pleistocene of Sardinia. _Crocidura_ occurs in the cavern-deposits of Madras. Shrews from the Miocene and Upper Eocene of Europe have been referred to _Sorex_ and the genus _Amphisorex_, which is a synonym of _Crossopus_.

_Family_ TALPIDÆ.

Allied to the _Soricidæ_, but distinguished by the presence of a zygomatic arch and auditory bulla in the skull, and by the form of the teeth. The eyes are very small, and in some species covered with skin; the ears are short and concealed by the fur; the fore limbs are generally more or less modified for digging; there is no symphysis pubis; the intestine has no cæcum; the tibia and fibula are united; and the unicuspidate first upper and lower incisors are not extended horizontally forwards.

This family is connected with the _Soricidæ_ by _Urotrichus_ and _Uropsilus_. All the members are limited to the temperate regions of Europe, Asia, and North America; and the majority of them are of fossorial habits, although a few are aquatic or cursorial. The family has been divided into two subfamilies by Professor Mivart, and since this arrangement has been very generally adopted it will be followed here. From the presence of intermediate forms like _Scaptonyx_ Dr. Dobson, in the second part of his _Monograph of the Insectivora_, has proposed a different arrangement, which, with the omission of some forms which are of not more than subgeneric value, is as follows:—

MYOGALÆ—_Myogale_. CONDYLURÆ—_Condylura_. SCALOPES { _Scapanus_. { _Scalops_. TALPÆ—_Talpa_. UROTRICHI { _Scaptonyx_. { _Urotrichus_. UROPSILI—_Uropsilus_.

Subfamily =Myogalinæ=.—Clavicles and humerus moderately elongated; manus without falciform bone.

_Myogale_.[553]—Dentition: _i_ ³⁄₃, _c_ ¹⁄₁, _p_ ⁴⁄₄, _m_ ³⁄₃; total 44. Feet webbed. Habits aquatic. This genus is represented by the two species _M. moschata_ (Fig. 289) and _M. pyrenaica_, of which the former is by far the largest member of the family, its total length being about 16 inches. Its long proboscis-like snout projects far beyond the margin of the upper lip; the toes are webbed as far as the bases of the claws; and the long scaly tail is laterally flattened, so as to form a powerful instrument of propulsion when swimming. This species inhabits the banks of streams and lakes in South-East Russia, where its food consists of various aquatic insects. _M. pyrenaica_, living in a similar manner in the region of the Pyrenees, is very much smaller, has a round tail, and a proportionally longer snout. Fossil remains of _M. moschata_ occur in the Norfolk Forest bed, and were originally described under the name of _Palæospalax_. The genus is also represented in the Middle and Lower Miocene of the Continent.

[Illustration: FIG. 289.—The Desman (_Myogale moschata_). ¹⁄₃ natural size.]

_Urotrichus._[554]—Dentition: _i_ ²⁄₁, _c_ ¹⁄₁, _p_ ⁴⁄₃ or ³⁄₄, _m_ ³⁄₃; total 36. Feet not webbed; manus broad. Habits fossorial. The Mole-Shrews, as these animals are called, are represented by _U. talpoides_ of the mountains of Japan and _U. gibbsi_ of North America. These two species are small and closely allied animals; the American form (which it has been proposed to separate subgenerically as _Neurotrichus_) having _p_ ³⁄₄.

_Uropsilus._[555]—Dentition: _i_ ²⁄₁, _c_ ¹⁄₁, _p_ ³⁄₃, _m_ ³⁄₃; total 34. Manus narrow; tail naked and scaly. Habits cursorial. The single species, _U. soricipes_, from the borders of Tibet, is a slate-coloured animal with the external form of a Shrew but the skull of a Mole.

Subfamily =Talpinæ=.—Clavicle and humerus very short and broad; manus with a large falciform bone.

A. First upper incisor much larger than the second (New World Moles).

_Scalops._[556]—Dentition: _i_ ³⁄₂, _c_ ¹⁄₀, _p_ ³⁄₃, _m_ ³⁄₃; total 36. Extremity of muzzle simple; hind feet webbed; tail short and nearly naked. Represented by three species in the United States.

_Scapanus._[557]—Dentition: _i_ ³⁄₃, _c_ ¹⁄₁, _p_ ⁴⁄₄, _m_ ³⁄₃; total 44. Extremity of muzzle simple. The two North American species of this genus resemble _Scalops_ in general characters, but have a dentition like _Condylura_. The habits are like those of the latter, and the right to generic distinction is doubtful.

_Condylura._[558]—Dentition: _i_ ³⁄₃, _c_ ¹⁄₁, _p_ ⁴⁄₄, _m_ ³⁄₃; total 44. Extremity of muzzle surrounded by filiform appendages. The Star-nosed Mole (_C. cristata_) derives its name from the star-like ring of appendages at the extremity of the muzzle, with the nostrils in the centre. The general contour is Mole-like, but the tail is nearly as long as the body, and the manus is somewhat less powerful, with its terminal phalanges not cleft. The length of the head and body is about 5 inches. This species is common in parts of North America, and forms tunnels in the ground like the Common Mole.

B. First upper incisor scarcely larger than the second (Old World Moles).

_Scaptonyx._[559]—Dentition: _i_ ³⁄₂, _c_ ¹⁄₁, _p_ ⁴⁄₄, _m_ ³⁄₃; total 42. Manus moderately broad, as in _Urotrichus_. Represented only by _S. fusicaudatus_ of Eastern Tibet, which may be regarded as connecting _Talpa_ with _Urotrichus_, having the head of the former and the limbs of the latter.

_Talpa._[560]—Dentition (usually): _i_ ³⁄₃, _c_ ¹⁄₁, _p_ ⁴⁄₄, _m_ ³⁄₃; total 44. Manus extremely broad.

This genus includes the true Moles, of which the common English Mole[561] (_T. europæa_) is the type. This animal is about 6 inches in total length, of which rather more than one inch is occupied by the tail. The body is elongated and cylindrical, and, owing to the very anterior position of the fore limbs, the head appears to rest between the shoulders; the muzzle is long and obtusely pointed, terminated by the nostrils, which are close together; the minute eye is almost hidden by the fur; the ear is without a conch, and opens on a level with the surrounding integument. The fore limbs are rather short and very muscular, terminating in broad, naked, shovel-shaped feet, with the palms normally directed outwards, and each with five subequal digits armed with strong flattened claws. The hind feet are long and narrow, and the toes are provided with slender claws. The body is densely covered with soft, erect, velvety fur, the hairs being uniform in length and thickness, except on the muzzle and short tail. The colour of the fur is generally black, with a more or less grayish tinge, or brownish-black, but various paler shades up to pure white have been observed.

The food of the Mole consists chiefly of the earth-worm, in pursuit of which it forms its well-known underground excavations. Its habits were many years ago studied and described by M. Henri le Court. Like many other mammals, the Mole has a lair to which it may retire for security. This consists of a central nest formed under a hillock, placed in some protected situation, as under a bank, or between the roots of trees. The nest, which is lined with dried grass or leaves, communicates with the main run by four passages, of which only one joins it directly, leading downwards for a short distance and then ascending again. The other three are directed upwards and communicate at regular intervals with a circular gallery constructed in the upper part of the hillock, which in turn communicates by five passages leading downwards and outwards with another much larger gallery placed lower down on a level with the central nest, from which passages proceed outwards in different directions, one only communicating directly with the main run, while the others, curving round, either soon join or end blindly. The main run is somewhat wider than the animal’s body: its walls are smooth, and formed of closely compressed earth, the depth varying according to the nature of the soil, but ordinarily from 4 to 6 inches. Along this tunnel the animal passes backwards and forwards several times daily, and here traps are laid by mole-catchers for its capture. From the main run numerous passages are formed on each side, along which the animal hunts its prey, throwing out the soil in the form of mole-hills. The Mole is one of the most voracious of mammals, and, if deprived of food, is said to die in from ten to twelve hours. Almost any kind of flesh is eagerly devoured by captive Moles, which have been seen by various observers, as if maddened by hunger, to attack animals nearly as large as themselves, such as birds, lizards, frogs, and even snakes; toads, however, they will not touch, and no form of vegetable food attracts their notice. If two Moles be confined together without food, the weaker is invariably devoured by the stronger. Moles take readily to the water, in which respect they resemble their representatives on the North American continent. Bruce, writing in 1793, remarks that he saw a Mole paddling towards a small island in the Loch of Clunie, 180 yards from land, on which he noticed mole-hills.

The sexes come together about the second week in March, and the young—generally from four to six in number—which are brought forth in about six weeks, quickly attain their full size.

[Illustration: FIG. 290.—Skeleton of Mole × ⅔ (lower jaw removed to show base of skull). _c_, Calcaneum; _c.h._, clavicular articulation of the humerus; _cl._, clavicle; _e.c_, external condyle of humerus; _f._, femur; _fb_, fibula; _fc_, falciform bone (radial sesamoid); _h_, humerus; _i.c_, internal condyle of humerus; _il_, left ilium; _i.p_, ramus of the ilium and pubis; _is._, ischium; _l.d_, ridge of insertion of latissimus dorsi muscle; _l.t_, lesser trochanter; _m_, manubrium sterni; _o_, fourth intercentral ossicle; _ol_, olecranon; _p._, pubis widely separated from that of the opposite side; _pa._, patella; _p.m._, ridge for insertion of pectoralis major muscle; _pt._, pectineal eminence; _r_, radius; _rb_, first rib; _s_, plantar sesamoid ossicle corresponding to the radial sesamoid (os falciforme) in the manus; _sc._, scapula; _s.h._, scapular articulation of the humerus; _t_, tibia; _u_, ulna.]

The Mole exhibits in the whole of its organisation a perfect adaptation to its peculiar mode of life. In the structure of the skeleton (Fig. 290) very striking departures from the typical mammalian form are noticeable. Thus the presternum is so much produced anteriorly as to extend forward as far as a vertical line from the second cervical vertebra, carrying with it the very short and almost quadrate clavicle, which is articulated with its anterior extremity and distally with the humerus; being also connected ligamentously with the scapula. The fore limbs are thus brought opposite the sides of the neck, and from this position a threefold advantage is derived: in the first place, as this is the narrowest part of the body, they add but little to the general width, which if increased, would lessen the power of movement in a confined space; secondly, this position allows of a longer fore limb than would otherwise be possible, and so increases its power; and, thirdly, although the entire limb is relatively very short, its anterior position enables the animal, when burrowing, to thrust the claws so far forward as to be in a line with the end of the muzzle, the importance of which is evident. Posteriorly, the hind limbs are similarly removed out of the way by approximation of the hip-joints to the centre line of the body. This is effected by inward curvature of the innominate bones at the acetabula to such an extent that they almost meet in the centre, while the pubic bones are widely separated behind. The shortness of the fore limb is caused by the great reduction in the length of the humerus, which has lost all resemblance to its normal shape. In addition to the usual articulation with the glenoid cavity of the scapula, the humerus also has a separate articulation with the extremity of the clavicle. The bones of the manus are enormously expanded laterally; this expansion being increased by the large sickle-like bone on the radial side of the carpus, which is considered by some anatomists to represent the prepollex. The skull is long and tapering, with very slender zygomatic arches and elongated nasals, which are ankylosed together, and in advance of which the mesethmoid is more or less ossified. The vertebræ are usually C 7, D 13, L 6, S 6, C 10-12; all having very strong surfaces for mutual articulation. The upper incisors are chisel-like, and the canine has two roots; the first three upper premolars are simple and conical, but the fourth is much larger, and canine-like. In the mandible the incisors are small and somewhat proclivous, while the canine can only be distinguished from them by its position: the first lower premolar is larger than the others.

The Common Mole has an exceedingly wide distribution, ranging over the greater part of the Palæarctic region, where it is met with in places so widely sundered as England and Japan. It occurs in both the Himalaya and Altai mountains. In Ireland it is unknown, and in Scotland it extends as far north as Caithness. Eight species of the genus are recognised, which may be grouped, from the characters of their dentition, as follows, viz.: _i_ ³⁄₃, _c_ ¹⁄₀, _p_ ⁴⁄₄, _m_ ³⁄₃, _T. wogura_; _i_ ³⁄₃, _c_ ¹⁄₁, _p_ ⁴⁄₄, _m_ ³⁄₃, _T. europæa_, _cæca_, _longirostris_, _micrura_; _i_ ³⁄₃, _c_ ¹⁄₁, _p_ ³⁄₄, _m_ ³⁄₃, _T. leucura_, _leptura_; _i_ ³⁄₃, _c_ ¹⁄₁, _p_ ³⁄₃, _m_ ³⁄₃, _T. moschata_.

Except in _T. europæa_, the eyes are covered by a membrane. In _T. micrura_ the short tail is concealed by the fur. _T. cæca_ is found south of the Alps; the remaining species are Asiatic, and two only—_T. micrura_ and _T. leucura_—occur south of the Himalaya. _T. moschata_, of Tibet, is regarded by some zoologists as generically distinct under the name of _Scaptochirus_.

Remains of _T. europæa_ occur in the Norfolk Forest bed, while extinct species are found in the European Tertiaries as far down as the Lower Miocene, although it has been proposed to separate some of these forms generically. _Protalpa_, of the Upper Eocene Phosphorites of Central France, is very closely allied, but the structure of the humerus is somewhat less specialised.

_Extinct Genera._—A number of extinct Insectivora from the European Tertiaries more or less closely allied to the Moles have been described, but since our knowledge of most of them is extremely imperfect their precise affinities are in many instances problematical. Of these, the Lower Miocene _Tetracus_ is said to have affinity both with _Myogale_ and _Erinaceus_; while the forms described as _Mysarachne_ and _Echinogale_, are considered to connect the present with the two preceding families. _Plesiosorex_ is another Lower Miocene type known only by the mandible, in which there are ten teeth; it is generally referred to the _Myogalinæ_. The minute _Amphidozotherium_, of the French Phosphorites, is considered to be allied to _Urotrichus_.

_Family_ ADAPISORICIDÆ.

This extinct family is represented by the genera _Adapisorex_ and _Adapisoriculus_, of the lowest Eocene of Rheims, which are regarded as allied to the _Soricidæ_, but somewhat more specialised. In the type genus the formula of the lower teeth is _i_ 2, _c_ 1, _p_ 4, _m_ 3; the incisors and canine being proclivous, and the molars (of which the last is small and without a third lobe) quadritubercular. _Adapisoriculus_ is a smaller form with differently shaped molars.

[Illustration: FIG. 291.—The last left upper cheek-teeth of _Pleuraspidotherium aumonieri_; from the Lowest Eocene of Rheims. _pr_, protocone; _me_, metacone; _pa_, paracone; _b_, cingulum-cusp. (From Osborn.)]

Here also may be mentioned the genera _Orthaspidotherium_ and _Pleuraspidotherium_, from the above-mentioned deposits, which are probably members of the present order. They appear to have been animals somewhat smaller than a Hedgehog, with quadritubercular upper molars (Fig. 291), and the hinder premolars more complex than those of the _Erinaceidæ_. In the first-named genus the dental formula is _i_ ³⁄₃, _c_ ¹⁄₁, _p_ ⁴⁄₄, _m_ ³⁄₃; the third and fourth upper premolars having one outer column. _Pleuraspidotherium_ has apparently only three premolars, of which the third and fourth (Fig. 291) have two outer columns. The humerus in both has no entepicondylar foramen, the femur has a third trochanter, and the astragalus is vertically perforated.

_Family_ POTAMOGALIDÆ.

Skull with a small brain-case, no zygomatic arch or postorbital process, and the tympanic annulate and not forming a bulla. Upper molars with the cusps arranged in a broad V, and somewhat intermediate in structure between those of the preceding and succeeding families. No clavicle; pubic symphysis ligamentous; tibia and fibula typically united distally. No cæcum. Confined to the Ethiopian region.

[Illustration: FIG. 292.—_Potamogale velox._ × ¼. (From Allman, _Trans. Zool. Soc._ vol. vi. pl. i.)]

_Potamogale._[562]—Dentition: _i_ ³⁄₃, _c_ ¹⁄₁, _p_ ³⁄₃, _m_ ³⁄₃; total 40. Represented only by _P. velox_ of Western Equatorial Africa. This animal (Fig. 292) inhabits the banks of streams, and is thoroughly adapted for an aquatic life; it is nearly 2 feet in length, the tail measuring about half. The long cylindrical body is continued uninterruptedly into the thick laterally compressed tail, the legs are very short, and the toes are not webbed, progression through the water evidently depending wholly on the action of the powerful tail, while the limbs are folded inwards and backwards. The muzzle is broad and flat, and the nostrils are protected by valves. The fur is dark brown above, the extremities of the hairs on the back being of a metallic violet hue by reflected light, beneath whitish. This curious animal was discovered by M. du Chaillu.

_Geogale._[563]—Dentition: _i_ ²⁄₂, _c_ ¹⁄₁, _p_ ³⁄₂, _m_ ³⁄₃; total 34. This genus is known solely by _G. aurita_, a small Mouse-like species from Madagascar, agreeing closely with _Potamogale_ in the general form of the skull and teeth. The tibia and fibula are distinct, but it is not known whether a clavicle exists; and the material at present available is insufficient to definitely fix the natural position of the genus.

_Family_ SOLENODONTIDÆ.

Skull with a small brain-case constricted between the orbits, no zygomatic arch or postorbital process, and the tympanic annulated and not forming a bulla. Upper molars tritubercular, the cusps being arranged in a V. Pubic symphysis short; tibia and fibula distinct. Vertebræ: C 7, D 15, L 4, S 5, C 23. No cæcum. The penis is carried forwards and suspended from the abdomen; the testes are received into perineal pouches; the mammary glands are post-inguinal; the uterine cornua end in cæcal sacs.

[Illustration: FIG. 293.—_Solenodon cubanus._ × ⅕ (From Peters, _Abh. Akad. Berlin_.)]

_Solenodon._[564]—Dentition: _i_ ³⁄₃, _c_ ¹⁄₁, _p_ ³⁄₃, _m_ ³⁄₃; total 40. This genus, with _S. paradoxus_ and _S. cubanus_ (Fig. 293), from Hayti and Cuba respectively, alone represents the family. These species, which differ chiefly in the colour and quality of the fur, have a remarkably long cylindrical snout, a long naked tail, feet formed for running, and the body clothed with long, coarse fur.

The position of the mammæ quite behind on the buttocks is unique among Insectivora. The first upper incisor is much enlarged, and this and the other incisors, canines, and premolars, closely resemble those of _Myogale_; the second lower incisor is, as in _Potamogale_, much larger than the anterior one, and is deeply hollowed out internally. While thus apparently showing relationship with the _Talpidæ_, the form of the crowns of the molar teeth connects them with the next family.

_Family_ CENTETIDÆ.

Skull (Fig. 294) with a small cylindrical brain-case not constricted between the orbits, no zygomatic arch or postorbital process, and the tympanic annulate and not forming a bulla. Upper molars tritubercular. Pubic symphysis short; and the tibia and fibula either united or free. No cæcum. The penis is pendent and retractile within the fold of the integument surrounding the anus; the testes are abdominal; the mammæ are thoracic and ventral; and the uterine cornua are terminated by the Fallopian tubes. All the species are limited to Madagascar.

[Illustration: FIG. 294.—Left lateral view of the skull of the Tenrec (_Centetes ecaudatus_). Reduced.]

Subfamily =Centetinæ=.—Tibia and fibula distinct; testes near kidneys; fur with spines.

_Centetes._[565]—Dentition: _i_ ²⁄₃, _c_ ¹⁄₁, _p_ ³⁄₃, _m_ ³⁄₃; total 38. Vertebræ: C 7, D 19, L 5, S 3, C 8. The single species is the well-known Tenrec (_C. ecaudatus_), characterised by the absence of a tail; it reaches a total length of from 12 to 16 inches, and is the largest known Insectivore. The adult males have long canines, the extremities of the lower pair being received into pits in front of the upper ones (Fig. 294). It is probably the most prolific of all mammals, since as many as twenty-one young are said to have been brought forth at a birth. The young have strong white spines arranged in longitudinal lines along the back, but these are lost in the adult animal, which is provided only with a nuchal crest of long rigid hairs. In rare instances a fourth upper molar may be developed.

_Hemicentetes._[566]—Dentition: _i_ ³⁄₃, _c_ ¹⁄₁, _p_ ³⁄₃, _m_ ³⁄₃; total 40. This genus is represented by the two species _H. semispinosus_ (of which the skull is shown in Fig. 295) and _H. nigriceps_. It differs from _Centetes_ by the presence of the third upper incisor, the much smaller canines, and by the form of the skull. Both species are very much smaller than _C. ecaudatus_, and the dorsal spines are retained in the adult state. Vertebræ: C 7, D 16, L 5, S 3, C 9.

_Ericulus._[567]—Dentition: _i_ ²⁄₂, _c_ ¹⁄₁, _p_ ³⁄₃, _m_ ³⁄₃; total 36. Vertebræ: C 7, D 17, L 6, S 4, C 9. The single species, _E. setosus_, is a Hedgehog-like animal, having the whole upper surface and the short tail densely covered with close-set spines. The facial bones are much shorter than in any of the preceding genera, and the first upper incisor is elongated, as in _Erinaceus_. Judging from the slight development of the cutaneous muscles compared with those of the true Hedgehogs, it is probable that complete involution of the body does not take place.

Subfamily =Oryzorictinæ=.—Tibia and fibula united; testes near urethra; fur without spines.

[Illustration: FIG. 295.—Skull of _Hemicentetes semispinosus_. × 2. (From Mivart, _Proc. Zool. Soc._ 1871.)]

_Microgale._[568]—Dentition: _i_ ³⁄₃, _c_ ¹⁄₁, _p_ ³⁄₃, _m_ ³⁄₃; total 40. This genus includes _M. longicaudata_ and _M. cowani_, both of which are small Mouse-like species, the former with a tail double the length of the head and body, and having 43 caudal vertebræ; teeth like those of _Centetes ecaudatus_, but, owing to the comparatively much shorter muzzle, not separated by wide spaces, and the last premolar and molar with internal basal processes.

_Oryzorictes._[569]—Represented by two species, _O. hova_ and _O. tetradactylus_, the latter distinguished by the presence of only four digits in the manus, the three inner having long laterally compressed fossorial claws. The general form of the head and body of the two species known is like that of a Mole. These animals burrow in the rice-fields and do much damage to the crops.

_Family_ CHRYSOCHLORIDÆ.

Skull conical, not constricted between the orbits, without postorbital process, but with well-developed zygomatic arch and tympanic bulla. Upper molars tritubercular, with the crowns very tall. No pubic symphysis; the tibia and fibula united. The eyes are covered by the hairy integument; the ears short and concealed by the fur; the internal generative organs are as in _Centetinæ_; the mammæ are thoracic and inguinal and placed in cup-shaped depressions. Habits fossorial. Confined to the southern part of the Ethiopian region, not extending to Madagascar.

This family is closely allied to the _Centetidæ_, occupying the same relative position with respect to that family that the _Talpidæ_ does to the _Soricidæ_. Compared with the _Talpidæ_, we find the following differences in the structural adaptation to a fossorial life; the manubrium sterni is not anteriorly elongated, neither are the clavicles shortened; but this is compensated for by a deep hollowing out of the antero-lateral walls of the thorax, the ribs in these parts and the sternum being convex inwards. The long clavicles have their distal extremities pushed forward, and the concavities on the sides and inferior surface of the thorax lodge the thick muscular arms.

[Illustration: FIG. 296.—The Golden Mole (_Chrysochloris obtusirostris_).]

_Chrysochloris._[570]—Dentition: _i_ ³⁄₃, _c_ ¹⁄₁, _p_ ³⁄₃, _m_ ³⁻²⁄₃₋₂; total 40 or 36. Vertebræ: C 7, D 19, L 3, S 5, C 8. This genus includes some seven or eight South African species, commonly known as Golden Moles (Fig. 296). Those species, in which the molars are reduced to ²⁄₂, with a basal talon to the lower ones, and without a prominence in the temporal fossa, have been placed in a separate genus, _Chalcochloris_, by Professor Mivart. Nearly all the species have the fur of the upper surface of a brilliant metallic lustre, varying from golden bronze to green and violet of different shades. The manus has four digits, of which the two outer are small, while the middle ones are large, with immensely powerful claws.

_Extinct Types._—The only fossil forms which can be referred to the section of the Insectivora with tritubercular molars are the _Leptictidæ_, of the Eocene and Miocene of North America. This family includes the genera _Leptictis_, _Mesodectes_, and _Ictops_, all of which are regarded by Dr. Schlosser as true Insectivora, although they were placed by Professor Cope with the Creodont Carnivora.

_Bibliography of Insectivora._—Peters, _Reise nach Mossambique—Säugeth._ 1852; Id. “Ueber die Classification der Insectivora,” _Monatsb. Akad. Wissensch. Berlin_, 1865, and other papers; Mivart, “On the Osteology of Insectivora,” _Journ. Anat. and Phys._ 1867, 1868, and _Proc. Zool. Soc._ 1871; Gill, “Synopsis of Insectivorous Mammals,” _Bull. Geol. and Geog. Survey, U.S.A._ Washington, 1875 (includes a general bibliography of the order); Dobson, _Monograph of the Insectivora, Systematic and Anatomical_, London, 1882-90.