CHAPTER IX

CHELONIA–ATHECAE–THECOPHORA

_SUB-CLASS IV.–CHELONIA._

There is no mistaking a tortoise. The shell and the horn-covered toothless jaws separate them from all other four-footed creatures.

They may be described as terrestrial or aquatic, pentadactyle reptiles, with walking limbs or with paddles; ribs with capitular portions only, two sacral vertebrae, humerus with entepicondylar foramen, pubes and ischia forming symphyses, quadrate bones fixed, jaws without teeth, but with cutting horny sheaths. Trunk encased in a bony shell, composed of numerous dorsal and ventral dermal bones, forming a carapace and a plastron, which may or may not be covered with horny shields. Copulatory organ unpaired, cloacal opening more longitudinal than round, never transverse. Oviparous.

It is customary to distinguish the marine, paddle-limbed kinds as _Turtles_, the others as _Land-_ and _Water-tortoises_.

Tortoises occur already in the Trias. They reached their greatest development towards the end of the Mesozoic and in the earlier Tertiary periods. They are now comparatively reduced in the number of families and genera, although they are still represented by about 200 species. The sub-class as a whole is cosmopolitan, but does not occur in the colder regions.

Their origin is quite unknown. Of recent groups only the Crocodilia and the Rhynchocephalia come into consideration. Combination of these groups with the Chelonia leads to some unknown forms whence also the Theromorpha have arisen. Palaeontology does not help us, all the leading, main groups of Chelonia having been in existence in the earlier Mesozoic ages, {313}and Palaeozoic Chelonia are still unknown. We can, however, to a certain extent, reconstruct an ideal primordial Chelonian by assigning to it all the ancestral characters actually observed in recent and fossil kinds, and by reducing to simpler conditions those features which we know to be more or less exaggerated specialisations. It is reasonable to assume that originally each metamere, except those of the anterior half of the neck and the posterior half of the tail, carried a transverse series of dermal plates, covered with horny shields, while the trunk, according to the greater bulk of the body, increased in size, converging towards the root of the neck and tail. By concentration, reduction of the number, and increase in the size of some of the remaining plates and shields, the skull assumed its characteristic box-like shape, the neck and tail becoming at the same time free. Chelonia are without doubt descendants of terrestrial, or at least semi-aquatic reptiles, and the marine paddled forms subsequently developed from terrestrial kinds.

CLASSIFICATION OF CHELONIA.–After many vicissitudes it was recognised that the Chelonia cannot naturally be divided according to the modification of their feet. The TRIONYCHOIDEA were clearly separated from the rest by Stannius in 1854. Cope, in 1870, was the first to emphasise the important character of the mode in which the neck is either bent sidewards (PLEURODIRA) or withdrawn in an S-shaped curve in a vertical plane (CRYPTODIRA); and he also separated _Sphargis_ as ATHECAE from all the other Chelonians, for which Dollo in 1886 proposed the term THECOPHORA. The division of the latter into recognisable families, based upon reliable, chiefly internal, skeletal, characters, has been effected by Boulenger;[127] and his classification has been adopted in the present volume, after intercalation of the more important fossil forms. The relationships between these various families may perhaps be indicated as follows:–

{ ATHECAE Sphargidae { { { _Pleurodira_ { Pelomedusidae { { { Chelydidae–Carettochelydidae { { CHELONIA { THECOPHORA { _Cryptodira_ { Chelydridae–Dermatemydidae– { { { Cinosternidae { { { Platysternidae { { { Testudinidae–Chelonidae { { { { _Trionychoidea_ Trionychidae

{314}The guiding taxonomic characters are fully mentioned at the head of the different families, and are mostly internal. The following "key," adapted from Boulenger, and based upon external characters, is preferable for practical purposes.

_For the position and names of the horny shields_ see Fig. 61 on p. 315.

Shell covered with horny shields. Digits distinct, with 5 or 4 claws. Pectoral shields separated from the marginals by inframarginals. Tail long and crested. Plastron small and cruciform. North America _Chelydridae_, p. 338. Tail long, covered with rings of shields. Plastron large. Indo-China _Platysternidae_, p. 345. Tail short. North and { _Dermatemydidae_, p. 341. Central America { _Cinosternidae_, p. 342. Pectoral shields in contact with the marginals. Plastral shields 11 or 12, without an intergular. Neck retractile in an p. S-shaped vertical curve _Testudinidae_, p. 345. Plastral shields 13, an intergular being present. Neck bending sideways under the shell { _Chelydidae_, p. 399. { _Pelomedusidae_, p. 390. Limbs paddle-shaped, with one or two claws _Chelonidae_, p. 378. Shell without horny shields, covered with soft, leathery skin. Digits distinct, broadly webbed, but with only three claws _Trionychoidea_, p. 404. Limbs paddle-shaped. Shell composed of regular series of bony plates. Two claws _Carettochelydidae_, p. 404. Shell composed of very many small plates arranged like mosaic. No claws _Sphargidae_, p. 333.

The VERTEBRAE are, sometimes in the various regions of the same individual, amphi-, opistho- or pro-coelous, or even biconvex. Traces of the chorda remain longest in the middle of the centra. Intercentra occur regularly on the first two or three cervicals, and then again in the tail as paired or unpaired nodules, or as short chevrons. The latter occasionally fuse with the caudal end of their centra. Intercentral discs of fibrous cartilage occur regularly in the neck and tail. The ribs develop originally in the same transverse level with these discs, and frequently the anterior thoracic vertebrae retain this intercentral or intervertebral position throughout life. Farther back they often show a gradual change from the intercentral to a more central and ultimately {315}remarkable to a purely neural attachment. In all the Chelonia the ribs are devoid of the tubercular portion.

[Illustration: FIG. 61.–Various plastra and their horny shields. 1, _Testudo ibera_; 2, _Macroclemmys temmincki_; 3, _Cinosternum odoratum_; 4, _Sternothaerus nigricans_; 5, _Chelodina longicollis_; 6, _Chelone mydas_. _a_ or _an_, Anal shield; _abd_, abdominal shield; _f_ or _fem_, femoral; _g_ or _gul_, gular, unpaired in Fig. 3; _h_ or _hum_, humeral shield; _i_ or. _int.g_, intergular; _im_, infra-marginals; _m_, marginals; _p_ or _pect_, pectoral; _x_, in Fig. 1, inguinal shield constituting, with the axillary _xx_, the last trace of infra-marginals.]

The cervical vertebrae have no ribs, except mere traces in the shape of small nodules. On the tail the ribs are often large, and, when fused with their neural supports, look like transverse processes; the whole arrangement exactly resembles that of Crocodilia. The first pair of thoracic ribs, those borne by the ninth vertebra, are peculiar. They arise from the anterior portion of the centrum, are much reduced, sometimes to mere threads of bone, and lean against the anterior rim of the second pair of ribs, in many cases without reaching the carapace. The next following ribs, those of the tenth to the sixteenth vertebra, are intimately involved in the formation of the first to seventh costal plates. The ribs of the two sacral vertebrae sometimes remain quite distinct throughout life, just touching the upper {316}ends of the iliac bones; but since these find a much more effective support in the shell, the distal ends of the sacral vertebrae fuse with the eighth, or so-called last, pair of costal plates.

The neural arch of the ninth vertebra rests upon its centrum; but the neural arches of the other trunk-vertebrae, although long, rest upon two centra; retaining, like the ribs, their original intercentral position; and in most cases the neuro-central sutures remain throughout life. The atlas and the last cervical vertebra deserve special attention. In many tortoises, _e.g._ _Trionyx_, _Clemmys_, _Testudo_, the three constituent parts of the atlas, namely, the neural arch, the centrum, and the intercentrum or first pair of united basiventralia, do not ankylose, but remain loosely connected; and the first centrum, instead of forming an odontoid process, remains movably attached to the second centrum, although it sometimes carries, and fuses with, the second intercentral piece. In other tortoises, _e.g._ _Platemys_ and _Chelys_, however, all the parts of the atlas co-ossify and form a complete, solid vertebra which articulates by a concavo-convex joint with the centrum of the second vertebra. The normal number of cervical vertebrae is eight in all Chelonians. The first spinal nerve issues between occiput and atlas, all the others behind the neural arches of their vertebrae. The last, or eighth cervical, owing to the retractility of the neck, forms elaborate joints; its centre fits with a knob into a cup of the ninth, and its post-zygapophyses form broad, curved articulating concave facets for the reception of the anterior zygapophyses of the fixed ninth vertebra. In the Trionychidae the zygapophyses are most elaborate, and they alone articulate with the ninth vertebra, while the centra do not join, but remain, or rather become, separated by partial resorption. In the Chelonidae, in conformity with the non-retractile and short neck, all the cervical joints are much reduced.

[Illustration: FIG. 62.–1, The complete atlas of an adult _Trionyx hurum_. The second basiventral (white) is attached to the posterior end of the first centrum, which, not being fused with the second centrum, is not yet an odontoid process. 2, The complete atlas of an adult _Trionyx gangeticus_, still typically temnospondylous. 3, The first and second cervical vertebrae of an adult _Platemys_. 4, The complete atlas of a _Chelys fimbriata_.]

{317}[Illustration: FIG. 63.–Skull of _Chelone mydas_. A, from the left side; in B, the postfrontal and squamosal bones have been removed, and the broad expansions of the jugal, quadrato-jugal, parietal, and quadrate bones have been reduced in order to reduce the skull to more primitive conditions. _F_, Frontal; _J_, jugal; _L.o_, lateral occipital; _Mx_, maxillary; _Op_, opisthotic; _Pal_, palatine; _Par_, parietal; _Prf_, prefrontal; _Pro_, pro-otic; _Pt.f_, postfrontal; _Ptg_, pterygoid; _Q_, quadrate; _Qj_, quadrato-jugal; _S.o_, supra-occipital; _Sq_, squamosal.]

The SKULL (cf. Fig. 54, H, I, K, p. 280) agrees fundamentally with that of _Sphenodon_ and of the _Crocodilia_, but it is characterised by several special features. There are no ectopterygoids or ossa transversa; no lacrymal bones, no interparietal or pineal foramen; the vomer is unpaired and the nasal bones are mostly absent, unless they are fused with the prefrontals. The premaxillae are very small. The single vomer forms a septum between the choanae; and these are, except in _Sphargis_, ventrally roofed over by wings sent out by the palatines. The latter form a continuous bony roof to the mouth with the pterygoids, and these diverge posteriorly, being connected suturally with the quadrates, lateral and basi-occipital bones, and with the unpaired basi-sphenoid, which appears between the basi-occipital and the diverging pterygoids, but is in most cases to a great extent overlapped by the latter. The occipital condyle is distinctly triple; the basi-occipital sometimes helps to border the foramen magnum. The supra-occipital sends out a long vertical blade, directed backwards and generally projecting far over the neck, for the attachment of the powerful cranio-cervical muscles. The quadrate is very peculiar. Firmly attached, and hemmed in on nearly all sides by the neighbouring bones, it stands nearly vertically and forms a broad articulating surface for the mandible. Its posterior side shows either a transverse, horizontal groove, in which lies the columella auris, or the groove is transformed into a more or less closed canal. Moreover, the hinder lateral margin of the quadrate forms most of the tympanic frame; its margins being curved backwards, leaving in the Cryptodira, however, a {318}wide notch behind; in the Pleurodira this part of the quadrate is transformed into a trumpet, the wide rim of which, forming a complete ring, carries the tympanic membrane. The tympanic cavity thus formed often leads into a deep recess which extends beneath the squamosal towards the opisthotic and bears some resemblance to the intricate tympanic recesses which pervade that region of the Crocodilian skull.

Dorsally the quadrate is broadly overlaid by the squamosal, which frequently forms an arch with the parietal. Anteriorly the quadrate is connected through a variably sized quadrato-jugal with the jugal; and this, by joining the maxilla and postfrontal, helps normally to form the posterior rim of the orbit. All the bones which border the temporal fossa vary much in extent in the different groups of Chelonia. The extremes are represented by _Cistudo_ and _Geoemyda_, in which the bony infratemporal arch is absent, owing to the loss of the quadrato-jugal; and on the other hand by the Chelonidae and by _Sphargis_, in which the whole temporal region is covered over by an additional "false cranial" roof. This roof is produced chiefly by lateral wing-like expansions of the parietal and postfrontal bones, which meet the likewise much expanded jugal, quadrato-jugal, and squamosal bones. In the lower diagram of Fig. 63 (_Chelone mydas_) the squamosal has been removed, and the other bones have been reduced to their normal, or rather primitive condition, for comparison with the external view of the complete skull of the same animal. The lower diagram shows also the connexion of the pterygoid with a descending process of the parietal; this column, paired of course, usually contains a separate bone, the epipterygoid, the portion between _Ptg_ and _Par_.

The hyoidean apparatus is well developed, and sometimes assumes large dimensions, especially in _Chelys_. The two pairs of "horns" are the first and second branchial arches, whilst the hyoid arches are reduced to a pair of small, frequently only cartilaginous, nodules attached near the anterior corners of the basis linguae, which generally fuses with the os entoglossum in the tip of the tongue.

The PECTORAL ARCH consists of a pair of long coracoids sloping obliquely backwards, the distal cartilages of which scarcely touch each other in the middle line, and the scapulae. The upper end of the scapula frequently touches the inside of the {319}first costal plate, protected by a cartilaginous pad. Near the glenoid cavity arises a long process (PC in Fig. 65), placed transversely and approaching its fellow. The distal end is connected with that of the coracoid by a fibro-cartilaginous band. The homology of this scapular process is not quite clear. The band just mentioned favours the idea that the process represents the precoracoid, but its being an outgrowth from the scapula suggests that it is merely the much enlarged acromion. It certainly does not represent the clavicle, which forms part of the plastron: and this is not in contact with the shoulder-girdle at all.

[Illustration: FIG. 64.–Diagram of the skeleton of _Testudo elephantopus_, after removal of the left half of the carapace. The plastron is roughly indicated by a section through the middle line. _Fe_, Femur, foreshortened; _Fi_, fibula; _H_, humerus; _Il_, ilium; _Is_, ischium; _P.P._, pubis; _R_, radius; _Scap_, scapula; _Tb_, tibia; _u_, ulna; 3, third cervical vertebra; 1, 3, 5, first, third, and fifth fingers; _XIII_, thirteenth (fifth thoracic) vertebra.]

The PELVIS is strong. Ilium, pubis, and ischium meet at the acetabulum. The dorsal end of the ilium is generally broadened, and is attached to one or both sacral vertebrae, but it is also in contact with the superimposed last costal plate. This additional connexion often becomes predominant and the sacral vertebrae are partly or completely relieved of the iliac support, fusing in this case more or less with the costal plates. The pubes have strong lateral processes, directed obliquely forwards and downwards. The pubes and the ischia, which latter are much smaller, form broad symphyses, and these are connected with each other by a longitudinal cartilaginous band (_Chelone, Trionyx_); or the connecting bridge is broad and quite ossified (_Testudo_), forming in the latter case two roundish obturator-foramina. Cartilage frequently remains at the anterior end of {320}the pubic symphysis, and a smaller, longer, and narrow piece of cartilage extends sometimes backwards from the ischiadic symphysis, as the so-called hypo-ischium. In the Pleurodira the ends of the ilia, and those of the lateral processes of the pubes, are much broadened and firmly ankylosed with the posterior costal plates and with the xiphiplastron respectively.

[Illustration: FIG. 65.–Ventral view of the bony shell of _Chelone mydas_, the Green Turtle, after removal of the plastron (Fig. 66). The costal plates are marked by cross lines to distinguish them from the ribs. _C_, coracoid; _Fe_, femur; _Fi_, fibula; _H_, humerus; _Ma._1-_Ma._12, marginal plates, some of which are fused together; _Nu_, nuchal plate; _PC_, "precoracoid"; _R_, radius; _Sc_, scapula; _I_, _V_, first and fifth digits; _IX_, Ninth vertebra or first thoracic.]

The LIMBS are typically pentadactyle and complete, and are most primitive in water-tortoises, e.g. _Chelydra_ and _Emys_, in which the carpus consists of the typical ten separate elements, including the pisiform. In _Testudo_ the centrale is fused with the intermedium, and the first three distal carpals are also fused together. In the marine turtles the limbs are transformed into paddles, but all the bones retain their independence; the pisiform {321}and the first metacarpal are enlarged and flattened, thereby giving additional width to the paddle. The tarsus remains less primitive; the centrale and the proximal elements have a tendency to fuse together, most completely in land-tortoises; the fifth distal carpal is enlarged, and stands out hook-like from the rest. The number of the phalanges of the fingers and toes varies slightly. It is noteworthy that none of the Chelonia possess more than three phalanges. The three middle fingers and toes have mostly three phalanges; the pollex and hallux have always two; the number of phalanges of the fifth finger varies from three to one, of the fifth toe from two to none. The greatest reduction occurs in _Testudo_ and its allied genera of typical land-tortoises, _Homopus_, _Pyxis_, and _Cinixys_, the formula for the fingers being 2, 2, 2, 2, 2 or 1, and 2, 2, 2, 2, 0 for the toes. In _Pelomedusa_ all the fingers possess two phalanges only, owing to fusion of the first and second phalanges with each other.

[Illustration: FIG. 66.–The bones composing the plastron of _Chelone mydas_. On the right side the position of the covering horny shields[128] is indicated by dotted lines. _a_, Anal horny shield; _ab_, abdominal; _f_, femoral; _g_, gular; _h_, humeral; _ig_, intergular; _im_, infra-marginals; _p_, pectoral.]

The SHELL, which is the most characteristic feature of the Chelonia, consists of the dorsal "carapace" and the ventral "plastron." Each is composed of a considerable number of bony plates which arise as ossifications of nearly the whole thickness of the cutis, only a thin layer of subcutaneous connective tissue remaining soft and lining the inside of the shell. We restrict ourselves to a description of the shell of the Thecophora, leaving the discussion of the peculiar shell of _Sphargis_ to p. 336 f. Very young tortoises are still soft, and the plates which are beginning to ossify are not yet suturally united. The plastron (Figs. 66 and 67) consists of the paired epi-, hyo-, hypo-, and xiphi-plastral plates, and the unpaired endo-plastral plate.

{322}[Illustration: FIG. 67.–Bony shell of _Testudo ibera_. A, Ventral; B, dorsal; C, left-side view. In B, and on the right half of A, the position of the horny shields is indicated by dotted lines. The underlying bony plates are marked by strong lines. In B the 1st neural and costal plates, the 4th neural, costal, and 6th marginal plates, and the 7th neural plate are shaded. 1, 4, 6, First, fourth, and sixth neural plate; _M_, in C, fifth left marginal plate; _Nu_, nuchal plate.]

The latter is homologous with the interclavicle, the epi-plastra are homologous with the clavicles of other Reptiles, while the other pieces are genetically derived from, and are further modifications of, the so-called abdominal ribs of the Crocodilia and Prosauria, These plastral plates are never in direct contact with the shoulder-girdle or with any other parts of the internal skeleton. In the young of all tortoises, and in the adult of the Chelonidae and Trionychidae, the several plastral plates enclose large, irregularly-shaped fontanelles. These are more or less filled up in the other groups; and in the Testudinidae especially the whole plastron forms one continuous mass. The navel is situated between the hyo- and hypo-plastrals. Both these pairs are broader than the others, and are connected with the carapace by {323}means of several marginals. The connecting region is called the bridge. In several tortoises, e.g. _Emys_, the connexion with the marginals is formed by ligaments only and remains movable. In others, transverse, more or less perfect hinges are formed across the plastron. A rather imperfect joint between the hypo- and xiphi-plastrals develops with age in _Testudo ibera_. In _Cistudo_ and _Cyclemys_ a very effective hinge lies below the hyo- and hypo-plastrals, just in front of the bridge; and the anterior and posterior lobes of the plastron can be closed against the inner rim of the box, fitting tightly in _Cistudo_. In _Pyxis_ the front lobe only is movable.

[Illustration: FIG. 68.–A, Diagrammatic transverse section through the shell of _Testudo_. On the right side the horny shields have been removed, on the left are shown the neural, costal, marginal, and pectoral shields. The bony dermal plates are dotted. _Cap_, Capitular portion of rib; _Sp.C_, position of spinal cord. B, Vertical section through part of the shell, magnified and diagrammatic. B, Bony layer of the cutis; L, leathery layer of the cutis; M, cells of the Malpighian layer; P, star-shaped pigment-cells; SC, stratum corneum, composing the horny shields.]

The carapace is composed of one median series, a right and left lateral series of costal plates, and a series of marginals which surround the whole. The median series consists of one large nuchal plate, normally eight neurals and one to three supracaudal plates. The characteristic feature of the neural plates is that they are firmly fused with the broadened neural spinous processes of the underlying vertebrae. The nuchal plate lies in front of the first thoracic or ninth vertebra; it overlies the last cervical vertebrae, with the eighth of which it is connected by ligament only; but the posterior corner of the plate often fuses with the spine of the ninth vertebra. In the Chelydridae, and still {324}more in the Trionychidae, the nuchal sends out a pair of long rib-like processes, which either extend to below some of the neighbouring marginals, or their ends overlap those of the ribs of the second thoracic vertebra (e.g. _Trionyx_), or, lastly, they are in turn overlapped by the first costal plates (e.g. _Cyclanorbis_). Such rib-like processes are also present, well developed in the young, shorter in the adult, in the Dermatemydidae and Cinosternidae. It is possible that the nuchal plate represents the fused neural of the eighth and the costal plates of the ninth vertebrae. An indication of the compound nature of the nuchal may be found in the fact that two nuchals have been described in _Chelydropsis carinata_, a Miocene relation of _Chelydra_. Somewhat similar modifications have taken place in the post-sacral region. The one to three supracaudal plates are, namely, neurals which have lost their connexion with, or perhaps have never been fused with, the spinous processes of the movable tail-vertebrae. The number of neural plates is mostly eight, but there are sometimes individually nine or ten, the gradual suppression taking place first in the sacral region. When such a plate is suppressed the neighbouring costal plates usually close up and meet in the median line. In _Cistudo_, for instance, there are only seven normal neurals, the eighth pair of costals meet, and the original eighth neural is transformed into a supracaudal. In _Cinosternum_ the sixth to eighth costals meet, separating the one supracaudal widely from the remaining five neurals. The meeting of the last pair of costals, with co-ordinate reduction of the neurals to seven, is almost universal in the Pleurodira; and this tendency is carried out to an extreme in the Brazilian _Platemys_ and in the Australian _Chelodina_ and its allies, in which all the costals meet in the middle line, and the neurals are completely suppressed. Every stage intermediate between complete neurals (_Sternothaerus_) and interrupted, vestigial, and vanished neurals, is still represented by some genus. This process takes place independently, both in America and in Australia, and is one of the most recently introduced modifications.

The costal plates arise, like the neurals, independently in the cutis, but they soon come into contact with the underlying cartilage of the ribs, which are long enough to reach the marginals. The ribs flatten, become surrounded by the growing membrane-bone of the plates, and the cartilage of the ribs, {325}instead of ossifying, undergoes a process of calcification. Ultimately this is more or less absorbed, its place is taken by the dermal bone, which forms so to speak a cast of the rib, preserving in many cases the shape of the vanished rib, only the capitular portions of which remain unaffected. The number of costal plates is very constant, namely eight on each side, but some fossils have nine or ten, and there are still individual variations in recent forms, indicative of that number. In a large _Chrysemys concinna_ I find the last pair of costals clearly composed of at least two pairs, and this same specimen has nine distinct neural plates.

The marginal plates are originally paired, almost always eleven pairs, very rarely ten or twelve; an unpaired posterior plate, the pygal, is always present, and is probably the result of fusion. In the Chelonidae large fenestrae remain between the costal and marginal plates, only covered by leathery unossified cutis, and of course by the horny shields. In the Indian fresh-water genus _Batagur_ similar windows are gradually filled up with age, and the horny shields become extremely thin and almost confluent. On the other hand, in _Testudo polyphemus_, the bony shell, always very thin, becomes still thinner with age and finally fenestrated by absorption.

Great reduction has taken place in the carapace of the Trionychidae. The American species of _Trionyx_ have only seven pairs of costal plates; in _Cyclanorbis_ the neurals are reduced to two. The whole dorsal shell is much smaller than the body, and marginal plates are absent or merely vestigial. It is doubtful if the ossifications in the posterior half of the marginal flap of some genera are homologous with true marginals.

Externally the whole shell is covered, except in the _Trionychidae_, in _Sphargis_ and _Carettochelys_ with horny, epidermal shields. These are phylogenetically older than the dermal plates, and they do not correspond with them either in numbers or in position, although there exists a general resemblance in their arrangement. On the plastron we distinguish an unpaired or paired gular, and a pair of gular, humeral, pectoral, abdominal, femoral, and anal shields (Fig. 66). Sometimes there are also intergulars, paired in _Macroclemmys_ and _Chelys_, unpaired in _Chelone_; in many of the Pleurodira an unpaired intergular lies behind the gulars.

{326}The carapace of most Chelonians is covered with five neural, four pairs of costal and twelve pairs of marginal _shields_, the last of which often forms an unpaired pygal. In front of the first neural lies the nuchal shield, very variable in size, often absent. The Chelydridae, Dermatemydidae, Platysternidae, and Cinosternidae possess moreover several inframarginals, intercalated on the bridge between the marginal and some of the plastral shields. In many of the other families these inframarginals are restricted to the anterior and posterior corners of the bridge, as the so-called axillaries and inguinals, mostly small and variable. Lastly, _Macroclemmys_ has several small supramarginals.

There are consequently eleven longitudinal rows of shields in all; by elimination of the supra- and infra-marginals they are reduced to seven rows. It is absolutely certain that the number of transverse rows also was originally much greater than it is now. The mode of reduction of the number of the neural and costal shields has been studied in _Thalassochelys caretta_ (cf. p. 388.) The accompanying illustration (Fig. 69) shows some of the main stages actually observed in the reduction of these shields. The chief point is that certain shields are squeezed out, or suppressed by their enlarging neighbours. The ultimate result is the formation of fewer, but larger shields.

Each shield grows individually as follows. Every year, or rather during every periodically recurring period of growth, the area of the Malpighian layer belonging to each shield increases peripherally in size, and at the same time produces a new layer of horn. The original little shield, with which the tortoise is born, remains for years, often throughout life, as the so-called "areola;" it increases in thickness owing to the new layer of horn added from below, and peripherally the increase in size is indicated by the overlapping concentric rings. Each ring represents a year's growth, at least in tortoises which live in temperate zones, where hibernation means a complete suspension of growth. It is not known if the same applies to tropical species, which grow either throughout the year, or which undergo one or more periods of rest. The areola does not remain central; the growth is uneven. With age the oldest layers of the areola are frequently rubbed off, and the areola then appears enlarged.

{327}[Illustration: FIG. 69.–Diagrams illustrating the progressive reduction of the horny shields in various Chelonians. The shields, the fate of which it is desired to follow, are indicated by distinctive shading. I. Hypothetical, primitive stage. Eight neural (including the nuchal) and eight costal shields. Both neurals and costals lie in the same transverse planes. II.-VII. Successive stages in the reduction and suppression of various shields, observed in specimens of _Thalassochelys_, the normal condition of which is represented by VII. VIII. Six neurals and only four costals. The normal condition of _Chelone_. IX. The nuchal shield has become very small and the resulting gap has been filled up by an enlargement of the first pair of marginals. This is the normal condition of most Cryptodirous tortoises. X. The first marginals meet in front and the nuchal is either suppressed (X_a_[X^a in diag]), _e.g._ in several species of _Testudo_, or it is surrounded by the marginals (X_b_), _e.g._ in _Sternothaerus_. (From Willey's _Zool. Results_, 1899.)]

{328}For the first dozen years or so the annual rings can be easily followed, but when the creature approaches maturity each shield adds very little to its growth, and the rings become very fine, crowded and irregular. Only by careful counting and comparison of the rings on the costals, marginals, and plastrals, can a reliable average be arrived at. In some tortoises, e.g. _Chrysemys_, the whole outer layer of the shields peels off periodically; only a thin smooth layer like mica or tracing-paper remains, of course without any indication of rings. The pigment is formed in the Malpighian layer, but it frequently diffuses into the horny shields themselves, notably in _Chelone imbricata_, which yields the beautiful "tortoise-shell." The colour of the pigment is either black, yellow, or red, with resulting combinations. The green colour, often so beautiful in baby-specimens of _Chrysemys_, is optical, produced, according to Agassiz, by a network of black pigment, spread over a layer of yellow oil.

Horny scales, sometimes forming spines, and covering a nodule of dermal ossification, are also common on other parts of the skin, especially on the limbs of land-tortoises, and also on the tail of _Chelydra_. Sometimes the end of the tail is protected by a claw-like nail, for instance in _Pyxis_. In some of the gigantic land-tortoises, and in _Chelone mydas_, this nail assumes large dimensions, and several of the terminal caudal vertebrae are fused together into a regular urostyle. In some subfossil specimens of Mauritian tortoises, these ankylosed complexes are 12 cm. long and more than 5 cm. broad!

Before leaving the description of the shell, it is worth while to draw attention to the enormous correlative changes in other organs produced by this case. Nearly the whole organism has been altered. The hard, firm carapace has partly rendered the supporting functions of the vertebral column unnecessary or impossible. In many tortoises, especially in the large land-tortoises, the vertebrae and the capitular portions of the ribs are reduced to mere bony outlines; the reduction to thin paper-like bony lamellae proceeds with age. The iliac bones find a better support in the costal plates; the contact with the sacral ribs is given up, and these ribs fuse partly with the costal plates, or they are absorbed. The whole mass of muscles of the trunk is completely lost in the region of the shell, but traces of them exist in young specimens. Neck, limbs, and tail can in most cases be withdrawn and hidden in the shell. When this is not possible it is due to secondary changes. The neck is withdrawn either by being tucked away {329}sideways (Pleurodira[129]), or by being bent in an S-shaped curve in a vertical plane. In a left-sided profile-view of the animal, the head represents the tail of the S. The neck is withdrawn by long muscles, which are inserted into the ventral side of the middle of the neck, and extend in the shape of vertical ribbons far back into the shell, arising from the centra of some of the middle or even more posterior thoracic vertebrae.

Lastly, a few remarks on the PARTIAL REGENERATION, or the mending of injuries to the shell. If part of the horny covering is badly bruised, torn off, or rubbed through, or if part of the shell is crushed, the underlying portion of the bony plate becomes necrotic, and the horny covering also dies so far as its Malpighian layer is destroyed. Soon, however, the uninjured Malpighian cells, around the margin of the wound, multiply, grow into and beneath the injured portion of the bone, and form a new horny layer, casting off the necrotic portion. After several months the deficiency is patched up; new bone has grown in the deeper remaining strata of the cutis, and the outside is covered by a continuous horny layer, without, however, reproducing the original concentric moulding of the shields. In badly crushed shells sometimes almost one-third of the whole shell is thus cast off and mended within one or two years. The regeneration of the forcibly stripped-off shields of _Chelone imbricata_ is described on p. 386. Bitten-off tails and limbs, rather frequent occurrences in water-tortoises, are of course not reproduced, but the wounds are healed and covered again with scaly skin.

SENSE-ORGANS.–The EYE is by far the best developed sense-organ. It is comparatively small. The pupil is round. The iris is mostly dark in terrestrial forms, while in water-tortoises it is often brightly coloured, for instance pale yellow in _Chelodina_, greenish and mottled with black, pale grey, brown, etc., in various species of _Chrysemys_. _Cistudo_ presents a curious sexual dimorphism; the males have red, the females brown, eyes. The sclerotic wall contains a ring of numerous small ossified plates. There is no trace of a pecten. The eye is protected externally by the two lids and the nictitating membrane. In some water-tortoises, notably in _Chelodina_, the lower lid is transparent. Lacrymal and Harderian glands are present.

{330}The SENSE OF HEARING is apparently not very acute, although tortoises and turtles are frightened by noise, and can distinguish sounds; otherwise they would have no voice, which is very tiny and piping in most tortoises during the pairing season. In most water-tortoises the tympanic membrane is thin and quite exposed; in land-tortoises it is often thick and covered by the ordinary skin; lastly, in _Chelone_ the tympanic cavity is filled with a plug of the much-thickened skin, possibly in adaptation to the water-pressure when these creatures dive to considerable depths. The ossicular chain is mostly reduced to a long, bony, columellar rod.

The SENSE OF SMELL is well developed. All Chelonians carefully smell their food, in the air as well as under water. The individual predilection shown by many species for different kinds of animal and vegetable food,–since they are, for instance, able to distinguish between the various sorts of cabbage, cauliflower, sprouts, etc.,–proves that they possess a considerable amount of smell and taste.

Tortoises have a fine sense of touch; even the slightest tap on the shell is noticed, and the skin of the soft parts is extremely sensitive. Tickling of the sides of the tail, or of the hinder surface of a thigh, produces ridiculous scratching actions of the same or of the opposite foot.

The DIGESTIVE APPARATUS is simple. Only a few peculiarities need be mentioned. The tongue is mostly broad and soft; it cannot be protruded. The oesophagus of the Chelonidae is covered with many conical projections pointing towards the stomach. The latter is simple, except in _Sphargis_. The intestine is devoid of a caecum, but the difference between the small intestine and the rectum is very marked and often abrupt. The cloaca is very roomy. It contains the large copulatory organ, which is unpaired, grooved on its dorsal side, and is altogether constructed like that of the Crocodilia. The large bladder opens ventrally into the urodaeum, a recess of the cloaca; near its base open the urinary and genital ducts. Many water-tortoises possess also a pair of lateral thin-walled sacs, the so-called anal sacs, dorso-lateral diverticula of the walls of the urodaeum. These sacs, which have highly vascularised walls, are incessantly filled and emptied with water through the vent, and act as important respiratory organs. When such a water-tortoise, for instance an _Emys_ or a _Clemmys_, is suddenly taken out of the water, it squirts out a {331}stream of this water, which is not, as is generally supposed, the urine from the bladder.

The mode of RESPIRATION is interesting. The lungs are very complicated, highly-developed, spongy structures. They are attached by their whole dorsal surface to the inner lining of the shell. As they cannot expand through their own initiative, and since the shell has made costal and abdominal expansion impossible, the tortoise has to resort to other means of producing the necessary vacuum. This is done partly by the neck and the limbs, which act like pistons in being drawn in and out; partly by the greatly developed hyoidean apparatus, by which, when the neck is stretched out, the throat is alternately inflated and emptied, the air being swallowed, or pumped into the lungs. Additional respiration, besides that of the anal sacs mentioned above, is effected in various aquatic tortoises by slightly vascularised recesses of the pharyngeal region. Most Chelonians can exist for a very long time without breathing; sulky individuals remain for hours or days under water. _Cistudo_ can shut itself up for an equally long time. Nevertheless this and other land-tortoises easily get drowned.

All Chelonians lay white EGGS, round or oval, according to their kind, but the shape of the eggs of one set sometimes varies within the greatest limits. The shell varies from a parchment-like, flexible, scarcely calcareous cover to a hard, well-polished case. As a rule the eggs, imbedded in the ground, are hatched after a few months, but in some of the northern kinds, e.g. _Emys orbicularis_, the hatching is deferred until the next spring, the embryo's development being arrested during the winter. How such eggs, buried a few inches only below the surface, withstand the often very severe North German and Russian winter is a mystery. Whilst the plastron is generally flat, it is more or less concave in the males of many species, notably in _Testudo_, _Cistudo_, and _Emys_.

The general conclusions which can be drawn from the present GEOGRAPHICAL DISTRIBUTION of the Chelonia are as few and unsatisfactory as those applying to the Crocodilia, since all the main groups of Chelonians, and many more extinct families, occurred together in bygone ages in the same countries, for instance in Europe.

{332}[Illustration: FIG. 70.–Geographical distribution of Cryptodirous tortoises.]

[Illustration: FIG. 71.–Geographical distribution of Pleurodirous tortoises.]

The marine forms are naturally cosmopolitan, but the _Testudinidae_ are likewise cosmopolitan, except in the Australian region. The _Chelydridae_, now restricted to North and Central America, occurred formerly also in Europe. The _Pleurodira_, in Mesozoic times plentiful in Europe, India, and North America, are now restricted to South America, Australia, and Africa; the _Pelomedusidae_ to Africa, Madagascar, and South America; the _Chelydidae_ to South America and Australia. In the latter country all the Chelonians belong to the Chelydidae. The _Trionychoidea_, occurring since the Cretaceous epoch in North America, in Early and Mid-Tertiary times in Europe, are now restricted to North America, Asia, and Africa. The country richest in Chelonians is America; North and Central America together possessing representatives of all the families except the Pleurodira, and these we know to have died out there. The _Dermatemydidae_, {333}_Cinosternidae_, and Chelydridae are now restricted to the Nearctic sub-region (including Central America). Poorest in genera and species, all of them Chelydidae, is the Australian region, where no fossils of other families have yet been discovered. Europe, with its few Testudinidae, does not come into consideration; Asia has at least Testudinidae and Trionychidae, and in addition the solitary _Platysternum_ in Indo-China, representative of a family whose affinities with the Chelydridae again proclaim the validity of the Periarctic region.

[Illustration: FIG. 72.–Geographical distribution of Trionychidae and Chelydidae.]

ORDER I. ATHECAE.

_The vertebrae and ribs are not fused with, but are free from, the carapace, which consists of numerous small polygonal plates and is covered with leathery skin without any epidermal shields. The limbs are transformed into paddles. The neck is not retractile. Marine._

FAM. SPHARGIDAE.–_Sphargis_ s. _Dermatochelys coriacea_, the Leathery Turtle or Luth, is the only recent species and is the largest of all recent Chelonians. The biggest specimen in the national collection is about six feet and a half long, from the nose to the end of the shell, which latter is about four feet long; such a specimen may weigh half a ton. Agassiz, however, says that he has seen some "weighing over a ton." The general colour is dark brown, either uniform or with yellow spots. The Leathery Turtle has a wide distribution, ranging over all the intertropical seas, but it is rare everywhere; least so perhaps in the Western Atlantic from Florida to Brazil and in the Indian Ocean.

{334}[Illustration: FIG. 73.–_Sphargis coriacea_, the "Leathery Turtle," young specimens, ventral and dorsal views. × 1.]

According to Agassiz it breeds regularly every year in the spring on the Bahamas, on the Tortugas, and on the coast of Brazil, depositing its many eggs on the sandy shore like other turtles. Accidentally it visits the northern coast up to Long Island, and specimens, perhaps carried with the Gulf Stream, have been caught on the coasts of Europe, for instance off Dorsetshire. One was caught near Nantes in 1729, and is said to have made a terrible noise when being killed. This is perhaps the reason why Merrem in 1820 invented the generic name _Sphargis_, supposed to be derived from σφαραγέω (I make a noise). It has also been recorded from the Mediterranean. It seems to be entirely carnivorous, living upon Molluscs, Crustacea, and fish. The flesh is supposed to be unwholesome. It is a very curious fact that of this rare species only large specimens, besides a very few baby-turtles, are known or preserved in collections, while individuals of intermediate size, say from four inches to three feet in length, have never been recorded. If it were not for the fact that they are still known to breed, it would look as if the {335}species were dying out. Perhaps they are very shy, leading a pelagic life, diving at the least sign of danger, and coming near the land only for the sake of breeding.

The structure of _Sphargis_ is so peculiar in many respects that it deserves a somewhat full account. The neuro-central sutures persist on all the vertebrae. The eight cervicals are short. All the ten trunk-vertebrae carry ribs, and these, with the exception of the last, articulate between the centra and with the neural arches; the first and tenth ribs are short, the others are long and flattened, but not broad, with wide spaces between them. The tail is short, although it consists of about twenty vertebrae; these are devoid of chevrons.

The skull superficially resembles that of _Chelone_, chiefly owing to the completely roofed-in temporal region. The supraoccipital crest is rather short, covered completely by the parietals, the posterior margin of which is rounded off instead of forming, as in the Chelonidae, a long projecting triangular crest with the supra-occipital. The parietals are in broad contact with the postfrontals, posteriorly they are just reached by the squamosals. The quadrato-jugal is small, separated from the postfrontal by the meeting of the squamosal with the jugal. The quadrate is notched behind, and it separates the opisthotic from the squamosal. The basisphenoid is large and broad, extending far forwards so as to separate the pterygoids widely from each other except in their anterior portions, which, instead of sending a lateral arm to the jugal and maxillary, as in _Chelone_, are widely separated from these bones by the palatines. The choanae lie on either side of the anterior half of the vomer, and are not roofed over by ventral vomero-palatine wings.

The limbs and their girdles are essentially like those of the Chelonidae, but are not derivable from them. The most remarkable feature is the shell. The dorsal and ventral halves are directly continuous, forming one unbroken case all round, which is composed of many hundreds of little bony plates, irregularly polygonal, fitting closely into each other with their sutural edges, and giving the shell a beautiful mosaic appearance. On the dorsal side are a median row and three pairs of lateral rows of larger plates, and these form seven longitudinal blunt ridges which all converge towards the triangularly pointed tail-end of the shell. The ridges are not so much produced by thickened {336}or spine-like edges of the plates, but by the right and left halves of the plates being actually bent at an angle. This is most conspicuous at the sides of the shell where it passes into the ventral portion. The latter has two pairs of lateral and one median ridge. The whole shell has consequently twelve ridges. The mosaic plates are deeply imbedded in the cutis, being externally as well as internally covered or lined with dense leathery skin. The epiderm is thin, and shows no indications of horny scales. In young specimens the whole shell is soft and very imperfectly ossified, later on it is quite rigid, although comparatively thin. It is nowhere in contact with the internal skeleton, except by a nuchal bone, which by a descending process articulates with the neural arch of the eighth cervical vertebra.

The affinities of the Sphargidae and their position in the system are still debatable. Whilst some authorities, _e.g._ Cope, Dollo, and Boulenger look upon _Sphargis_ as the sole remnant of a primitive group in opposition to all the other recent Chelonia, Baur considered it the most specialised descendant of the Chelonidae. Dames agreed with him. Van Bemmelen has modified this view in so far as he regards _Sphargis_ as the most specialised Chelonian, but considers the differences between it and the Chelonidae great enough to conclude that both Sphargidae and Chelonidae represent two independent, partly parallel, branches which have arisen from two different groups of terrestrial tortoises. Case,[130] from the study of _Protostega_ and other fossil forms, tends towards Baur's view. He believes that _Sphargis_ is the culminating form of a branch which through _Psephophorus_ and with _Eosphargis_ has sprung from some creature like _Lytoloma_, which at the same time is the starting-point of another branch which culminates in the genera _Thalassochelys_ and _Chelone_, while lastly a third branch contains _Protostega_, _Protosphargis_, and _Pseudosphargis_. In other words, he considers them all Chelonidae. If he is right we have of course no business to separate _Sphargis_ with its fossil allies from the rest of the Chelonia as "Athecae."

However, Case has not proved his point. It is easy enough to understand that the characters of the cranium and plastron of _Sphargis_ are in a condition which by partial reduction can be derived from that of typical Chelonidae. The structure of the {337}cervical vertebrae, the absence of the marginal plates and the peculiar articulation of the nuchal with the last cervical vertebra can be explained as convergent analogies, just like the paddles of _Carettochelys_. But the shell of _Sphargis_ is fundamentally different from and not homologous with that of the others. Cope was therefore quite justified in distinguishing the Sphargidae as "Athecae" in opposition to the others which Dollo later on, by contrast, named "Thecophora." Unfortunate names, since both groups are undeniably in possession of a θήκη or shell. Both authors meant, however, by Theca the epidermal shields, but even this distinction is rendered invalid by _Carettochelys_.

The most reasonable explanation has been suggested by Hay.[131] The mosaic polygonal components of the shell of _Sphargis_ are, so to speak, an earlier generation of osteodermal plates than the later generation of longer and broader bony plates which in the Thecophora come into contact, and fuse with, the neural arches and ribs. The osteoderms of _Sphargis_ belong to the same category as the dermal ossifications in the scutes of Crocodilia, whilst the plates of the carapace and plastron of the Thecophora belong to the category of the abdominal ribs. _Sphargis_ has the first kind in its peculiar shell, the second kind in the deeper lying plastron and in its nuchal plate. But it has lost, or perhaps had never developed, the horny shields. The only difficulty is, however, the presence of a plastron and of a typical neural plate in _Sphargis_. This difficulty is not very serious. The plastron is a very old institution. It occurs together with the more superficial osteoderms in _Caiman_, and the nuchal plate may be the oldest of all dorsals. We can scarcely imagine that the direct ancestors of _Sphargis_ had developed both kinds of shells, and that comparatively recently the inner shell of the carapace was lost, leaving only the nuchal plate. Fossils do not support such an assumption. Undoubted ancestral forms of _Sphargis_ are very rare. _Psephophorus_ of the Oligocene and Miocene of Europe had a continuous mosaic shell much resembling that of _Sphargis_; _Eosphargis_ is represented by a well-preserved skull from the London clay. Then follows a wide gap until we come to _Psephoderma_ of the Rhaetic, or Upper Trias of Bavaria; the large fragment of whose dorsal shell is composed of about 200 mosaic pieces. If this fragment really formed part of the shell {338}of a Chelonian, its age would speak greatly in favour of the Athecae being a very primitive and independent group.

ORDER II. THECOPHORA.

_Thoracic vertebrae and ribs united with a series of median or neural and a paired series of lateral or costal plates. Parietals prolonged downwards, meeting the pterygoids directly or by interposition of an epipterygoid._

SUB-ORDER 1. CRYPTODIRA.–_The carapace is covered with horny shields. The neck, if retractile, bends in an S-shaped curve in a vertical plane. The pelvis is not fused with the shell._

FAM. 1. CHELYDRIDAE.–The plastron is small and cross-shaped (Fig. 61, 2, p. 315); the bridge is very narrow, and the displaced abdominal shields are widely separated from the marginals by a few irregularly shaped inframarginals. The tail is long. The limbs, neck, and head are so stout that they cannot be completely withdrawn into the shell. Snout with a powerful hooked beak. American; only two genera, each with one species.

The temporal region is roofed very incompletely and only anteriorly by the expanded parietals and postfrontals, which form a long suture. The plastron consists of nine bony plates, a small entoplastron being present; there are lacunae in the middle line, the plates meeting imperfectly, and the horny abdominal shields are likewise separated by soft skin. The carapace has a nuchal with long rib-like processes which underlie the marginals; the neural plates form a continuous series. There are twenty-three marginal plates. The pubic and ischiadic symphyses remain separate, enclosing one large heart-shaped foramen. The five fingers and toes are webbed and are protected by claws except the outer toe, the nail of which is usually suppressed.

_Chelydra serpentina_, the Snapping Turtle, attains a large size, namely, a shell-length of more than one foot, and a total length from the nose to the tip of the tail of more than three feet. Its range extends from the Canadian lakes east of the Rocky Mountains, through the United States and Central America. The carapace of young specimens has three very marked series of keels, which gradually disappear with age, until in very old individuals the shell becomes quite smooth. The skin is very warty, especially on the neck, and there is a pair of minute {339}barbels on the chin. The tail carries three series of originally triangular horny crests, which with age are transformed into blunt knobs. The general colour of this rather ugly creature is olive, mottled with dark brown above and with yellowish below.

According to Holbrook the Snapping Turtle is found in stagnant pools, or in streams where the waters are of sluggish motion. Generally they prefer deep water, and live at the bottom of rivers; at times, however, they approach the surface, above which they elevate the tip of their pointed snout, all other parts being concealed; and in this way they float slowly with the current, but if disturbed they descend speedily to the bottom. They are extremely voracious, feeding on fish, reptiles, or any animal substance that falls in their way. They take the hook readily, whatever may be the bait, though most attracted by pieces of fish; in this way many are caught for the market. It is, however, necessary to have strong hooks and tackle, otherwise they would be broken, for the animal puts forth great strength in his struggles to escape, both with his firm jaws and by bringing his anterior extremities across the line. When caught they always give out an odour of musk, which in very old animals is sometimes disagreeably strong.

Occasionally the Snapping Turtle leaves the water, and is seen on the banks of rivers or in meadows, even at a distance from its accustomed element. On land his motions are awkward; he walks slowly, with his head, neck, and long tail extended, elevating himself on his legs like the Alligator, which at that time he greatly resembles in his motions; like the Alligator also, after having walked a short distance, he falls down to rest for a few moments, and then proceeds on his journey. In captivity they prefer dark places, and are exceedingly ferocious; they will seize upon and bite severely anything that is offered them, and their grasp upon the object with their strong jaws is most tenacious.

The Snapping Turtles, or "Snappers," are feared on account of the ferocious bites which they inflict, and they are hated because of the destruction of valuable fish and water-fowl. They in turn atone for this damage by being eaten, especially the younger half-grown individuals, the flesh of the older ones being too much tainted with the odour of musk. The round eggs, which are laid to the number of twenty to thirty in the summer {340}(in the Northern States about June), are likewise good to eat. The first act of the young creature on leaving the shell is said to be snapping and biting. In captivity they are often very sulky, and refuse food stubbornly for many months, perhaps for a whole year, and apparently without much harm to themselves, since they lie quietly in the distant corner of the tank, now and then slowly rising to the surface to breathe. Fresh-water algae grow on the shell and in the mud which settles on it, and since this happens also in the wild state, they are rendered as inconspicuous as old rotten logs. In order to attract fishes they protrude a pair of worm-like, pale pink filaments from the tip of the tongue.

[Illustration: FIG. 74.–_Macroclemmys temmincki_, "Alligator Turtle." × ⅙.]

_Macroclemmys temmincki_, the "Alligator Turtle."–In size and general appearance much like the other Snapping Turtle, but the dorsal shields have each a strong and prominent keel, and these three series increase in size with age. The costal shields are separated from the marginals by an additional series of about four supramarginals, well shown in the illustration. The shields of {341}the cross-shaped plastron are subject to much individual variation, small shields being frequently intercalated, or rather retained, between the usual ones, especially between the pectorals and abdominals, in the gular region, and on the narrow bridge, where the inframarginals number one to three or even more. This species inhabits, broadly speaking, the whole basin of the Mississippi and Missouri rivers.

This beast is as vicious as the other Snapping Turtle. According to Agassiz it does not withdraw its head and limbs on the approach of danger, but resorts to more active defence. It raises itself upon the legs and tail, highest behind, opens the mouth widely, and throwing out the head quickly as far as the long neck will allow, snaps the jaws forcibly upon the assailant, at the same time throwing the body forward so powerfully as often to come down to the ground when it has missed its object.

It lives mostly in the water, but makes considerable journeys overland. Both in the water and on dry land the limbs move nearly perpendicularly, and the body is raised high. On dry land a considerable part of the weight of the body is borne by the long, strong tail.

"They are as ferocious as the wildest beast of prey, but the slowness of their motions, their inability to repeat the attack immediately, their awkwardness in attempting to recover their balance when they have missed their object, their haggard look, and the hideous appearance of their gaping mouth, constitute at such times a picture as ludicrous as it is fearful and revolting. Their strength is truly wonderful. I have seen a large specimen bite off a piece of a plank more than an inch thick. They take hold of a stick with such tenacity that they may be carried for a considerable distance suspended to it free above the ground. Fishes and young ducks are their ordinary prey. They lay from twenty to forty or more round eggs only about the size of a small walnut in holes which they dig in sloping banks not far from the water" (Agassiz).

FAM. 2. DERMATEMYDIDAE.–The pectoral shields are widely separated from the marginals by inframarginals, the gular shields are very small or absent, and the tail is extremely short. Only two or three genera, with three or four species in Central America.

The plastron is composed of nine plates. In _Dermatemys mawi_ it is large, firmly joined to the carapace, covered with {342}eleven or more shields, and there are four inframarginals; in _Staurotypus salvini_ of Mexico the plastron is cruciform, with the anterior lobe movable, covered with seven or more shields, according to the fusion of the anal shields and the presence or absence of the gulars; there are only two inframarginals. The pubic and ischiadic symphyses remain separate; the temporal fossa remains widely open, the postfrontals scarcely touching the parietals. There are 23 marginal shields in _Staurotypus_, 25 in _Dermatemys_, including the unpaired nuchal. The nuchal plate has a pair of rib-like processes like those of the Chelydridae, but some of the posterior costal plates, sometimes only one pair, meet in the middle line, overlying or suppressing the corresponding neural plates. The shell of these aquatic tortoises is rather flat, more or less keeled, especially in young specimens, and in the fully adult condition is about one foot in length.

FAM. 3. CINOSTERNIDAE, represented by the single genus _Cinosternum_, with about ten species in North and Central America, and one in Guiana. Closely allied to the two previous families, with which it agrees by the separation of the pubic and ischiadic symphyses, the presence of an ento-plastral plate, the possession of inframarginal shields (Fig. 61, 3, p. 315), the widely open temporal fossae, and the rib-like pair of processes to the nuchal plate. It agrees with the Dermatemydidae in the interruption of the neural plates by the meeting of several pairs of the costal plates. There are 23 marginal shields; five or four shields, according to the presence or absence of the gular on the plastron, and in some species these plastral shields become, with age, more and more separated from each other by soft skin (see Fig. 75). The shape and size of the plastron differ considerably in the various species; in most of them, e.g. in _C. pennsylvanicum_ and _C. leucostomum_, but not in _C. odoratum_, the anterior and posterior lobes are movable, with transverse soft hinges, so that the animal can completely close its shell. The skin of the legs and neck is so baggy and loose that these parts slip in, the skin rolling off, when the creature withdraws into its shell. They lay only a few–from three to five–elliptical eggs, which have a shining, glazed, and thick, but very brittle shell.

{343}[Illustration: FIG. 75.–_Cinosternum odoratum_, young specimens. × ⅔. A and B, males; C, female.]

_Cinosternum odoratum_, the Mud-Turtle, or Stinkpot Terrapin, so called on account of the disagreeable smell which exudes from the inguinal glands. The head is disproportionately large, with the snout rather compressed laterally, and pointed underneath, with several short barbels. The neck is long and slender. The carapace of the young is keeled, each of the neural shields being raised in the middle line; but in full-grown specimens the shell becomes quite smooth and rounded. The horny shields of the plastron are relatively largest in the young, but they soon leave ever-increasing spaces between them, which are then filled with soft skin only, which thinly covers the underlying bone. The {344}fore- and hind-limbs, especially the latter, are extensively webbed, and are provided with five short claws. The general colour of the shell is horny brown, either uniform or with darker spots or streaks. The neck and limbs are mottled brown. The only ornamental colouring is a pair of clear yellow broad lines on each side of the head, and a similar streak on each side of the lower jaw. On the chin and upper throat are two pairs of small tentacles. The tail of the male is of about the length of the hind-limbs, while that of the female is so short that its tip scarcely reaches beyond the hinder margin of the carapace. Length of the shell of full-grown specimens between four and five inches. Very young specimens have a rather droll appearance, owing to the long and slender neck with the large head, and the humpy back.

This species is common in the eastern half of North America, from Canada to Texas. It is mainly aquatic, and is one of the dullest and shyest species. My own specimens spend most of their time in the water, invariably in the darkest corners, preferably under a stone or a log, and they do not leave their hiding places until dark, in search of worms, meat, and all sorts of animal food. For months I could never induce them to take food from a stick, or even to eat in my presence, and it was not until after many weeks that one of them at last protruded its head far enough to exhibit the yellow stripes. When taken out of the water they draw in their heads, just allowing the vicious little eyes to be visible, and opening the sharp-edged mouth widely to bite deliberately and furiously at the unwary finger. Some spent the winter in the water, in the greenhouses, feeding as usual, others crept on land, hiding under moss, half buried in the soil, where they slept for several months, but with interruptions in order to soak and to drink. When spring is well advanced they prefer the water for their regular sojourn. Some which had been sent over from New York arrived in a deplorably dried-up condition, the skin being quite flabby and shrivelled, but after a few hours' soaking they came round, and increased considerably in weight, the limbs and neck becoming turgid.

_C. pennsylvanicum_ of Eastern North America has a larger, more oval plastron. The head is not so strikingly large as in the other species and, like the neck, is brown with yellowish spots, and often has streaks on the sides. The tail of the male ends in a {345}nail-like horny point. The lobes of the plastron are well hinged in the adult.

_C. leucostomum_ of Central America is larger, with a shell-length of six inches. The plastron is not at all cruciform, but has a broad bridge, and fills the box, moreover it has an anterior and a posterior hinge, so that the box can be completely closed. Hence the vernacular name of the Box-Terrapin.

FAM. 4. PLATYSTERNIDAE, represented by the single species _Platysternum megacephalum_ in Burma, Siam, and Southern China.

The pectoral shields are widely separated from the marginals by inframarginals, the plastron is large, oblong, not cruciform, and the tail is long.

The plastron consists of nine plates, and is covered with six pairs of shields, the most anterior of which are the broad gulars. The nuchal plate has no rib-like processes. The neurals form a continuous series, and there are twenty-three marginal scutes. The temporal fossae are completely roofed over, owing to the long sutures formed by the parietals with the postfrontals, moreover the postfrontals expand laterally so much that they posteriorly come into broad contact with the quadrato-jugals and squamosals, anteriorly with the maxillaries, so that the jugals are completely surrounded by bones, and are shut off from the orbits and from the temporal fossae. This is a unique arrangement, found nowhere else in Tortoises. The pubic and ischiadic symphyses are connected with each other by ligaments only.

The general appearance of this water-tortoise is rather curious, since the carapace is much depressed, looking, especially in younger specimens, as if it had been crushed in. The head, provided with very strong hooked jaws, is strikingly heavy and large, and is covered above with one single large shield. The tail is longer than the shell, which, in full-grown specimens, reaches about six inches in length; it is, throughout its length, covered with rings of squarish shields. A large specimen measures 14 inches in total length, of which only five fall to the shell.

FAM. 5. TESTUDINIDAE.–The shell is always covered with well-developed horny shields. Those which form the plastral bridge are in direct contact with the marginals. The plastron is composed of nine bones. The digits have four or five claws. The neck is completely retractile. The skull is devoid of parieto-squamosal arches.

{346}This large family is cosmopolitan, with the exception of the Australian and the adjoining Austro-Malayan countries. It contains genera which form a continuous gradation between absolutely terrestrial and thoroughly aquatic tortoises; and many are truly amphibious. As a general rule the typically terrestrial kinds have a more curved or arched shell, the digits are short, the eggs are more oval or round, and they are chiefly herbivorous; the essentially aquatic kinds have a flatter or depressed shell, webbed feet, with longer, often slender claws, the eggs are more cylindrical, and they live on animal diet. About 20 genera, with more than 110 species, are recognised by Boulenger, but their essential characters are nearly all internal, and therefore of no avail for the determination of live or entire specimens.

_Chrysemys._–One of the most typical and widely distributed genera of American Terrapins or water-tortoises. The carapace is flat; the plastron is quite immovable, with a strongly developed bridge. Feet well webbed. Tail short. Skull with a broad, complete, lateral, temporal arch. About one dozen species, mostly in the eastern half of the United States, but the whole genus ranges from Canada to Argentina.

Most of the young _Chrysemys_ are very pretty, the ground-colour of the upper shields being green, variegated with yellowish-brown or blackish markings, which often form exquisitely delicate patterns, either concentrical (_Ch. concinna_, _Ch. rubriventris_), or more longitudinal (_Ch. elegans_), or apparently quite irregular. The ground-colour of the plastron is yellow, but the various species are best distinguished, at least in very young individuals, by the arrangement of the dark brown spots and patches. There are, for instance, several pairs of bold lateral and several median patches in _Ch. rubriventris_; five pairs of ocellated spots in _Ch. elegans_; only small median patches, where four plastral shields meet, in _Ch. concinna_; while the plastron of _Ch. picta_ is uniformly yellow.

These water-tortoises are very lively and shy, most so perhaps _Ch. picta_, which is very quick and active. The food varies, often according to individual fancy. Most of them eat fish. _Ch. picta_ is partial to insects, but it also takes worms. Some of my specimens refused meat for a long time, but ultimately they became so fond of it and of worms, that they came out of the pond to take the food from the fingers; those in the Zoological {347}Gardens of London have developed a taste for biscuits. One of my largest _Ch. concinna_ fasted deliberately for eight months, refusing worms, insects, meat, and frogs, only occasionally sniffing at the food, until it was tempted with whitebait, which it took greedily. It refused, however, smelts and pieces of soles, but after another month it condescended to take meat regularly. Very young individuals live chiefly on flies, which they watch for near the surface of the water; and they are fond of smooth caterpillars, maggots, the larvae of humble-bees, and similar soft creatures. They all spend most of their time in the water, preferably floating near the surface, hidden between weeds; and they are fond of basking. Some of them spend the night in the water, lying motionless on the bottom, with heads and limbs turned in. Others prefer hiding under moss. Those species, which, like _Ch. concinna_ and _Ch. picta_, are common in the North, are of course perfectly hardy. For the winter they dig themselves holes in the banks near the water, and they do not come out again until the spring is well advanced. The eggs are hard-shelled, mostly long and oval, and they are hatched before the end of the summer. The larger species of Terrapin are eaten.

_Ch. picta_ (Fig. 76), the "Painted Terrapin," of the Eastern United States, _e.g._ of New York and Long Island, is easily recognised by the much depressed shell, which is absolutely smooth, and without a trace of a keel. The colour above is dark olive-brown or blackish, with broad yellow bands across the anterior ends of the neural and costal shields. Three or four of these transverse bands are very conspicuous. The marginals are red, with more or less concentric black and yellow markings. The pretty red colour, with some black stripes, extends over the bridge, but the plastron itself is uniformly yellow. The soft parts are likewise prettily marked, the ground-colour is black-brown, with delicate bright yellow and red stripes on the sides of the neck, limbs, and tail. The stripes are originally yellow, but they develop an orange or red line in the middle, so that each red stripe is ultimately narrowly edged with yellow; or the yellow and red stripes alternate, for instance on the tail, which is short, narrow, and pointed. The head is further adorned with a pair of conspicuous bright yellow patches behind the eyes, and a smaller pair on the occiput. The black and yellow stripes run across the gape of the mouth, some of the lines even looking as if they had been {348}painted across. The nuchal shield is elongated and very narrow, its anterior edge and that of the neighbouring marginals are finely serrated. Very young individuals are at once recognised by the prominent longitudinal median stripe of bright orange extending over the nuchal and neural shields; the yellow transverse bands are still absent; they appear when the longitudinal line vanishes.

[Illustration: FIG. 76.–_Chrysemys picta_, "Painted Terrapin." × ½.]

The "Painted Terrapin" is one of the few species of which, thanks to L. Agassiz,[132] complete data of growth from the new born to old age are known. During the first six or seven years the rate of growth is so uniform that numerous specimens collected at the same time are readily arranged in sets of the same age, simply by the differences they show in their size. The successive lines of growth on the shields indicate the number of years. After the seventh year the age is much more difficult to distinguish in those tortoises, which, like _Ch. picta_, have a perfectly smooth epidermis. This smoothness is due to the fact that the shields undergo a process of moulting. An upper, quite {349}transparent layer of each shield peels off completely like a piece of mica. I have been able to confirm Agassiz' statement on _Ch. concinna_ in their third and fourth springs, and on a number of adult _Ch. picta_. The latter were not allowed to hibernate, being kept in a warm tank; they peeled completely during the late autumn, and then the red and yellow colours underlying the newly formed shields appeared very vividly; others moult at midsummer.

Growth of _Ch. picta_, after Agassiz.

+––––––––––––––––––––––+––––––––––-+––––––––––––+––––––––––-+––––––––––-+ | Year. | Length of | Breadth of | Height of | Length of | | | carapace. | carapace. | box. | tail. | +––––––––––––––––––––––+––––––––––-+––––––––––––+––––––––––-+––––––––––-+ | | millim. | millim. | millim. | millim. | | Second | 26.5 | 25 | 12 | 16.5 | | Third | 42 | 39.5 | 17 | 17.5 | | Fourth | 51 | 49 | 21.5 | 20.5 | | Fifth | 54 | 51 | 23.5 | 21.5 | | Sixth | 59 | 56 | 25 | 23.5 | | Seventh | 66 | 60 | 26.5 | 26 | | Eighth (♂) | 72.5 | 61 | 28 | 27.5 | | Ninth (♂) | 74 | 62 | 28 | 27.5 | | Tenth (♂) | 77 | 64 | 30 | 28 | | Eleventh (♂) | 80 | 67 | 30 | 28.5 | | Fourteenth (♂) | 92 | 74.5 | 33 | 28.5 | | Twenty-fifth (♀) | 121 | 92 | 43 | 34 | | Old ♀ | 129 | 96 | 47 | 37 | | Very old ♀ | 163 | 113 | 59 | 53 | +––––––––––––––––––––––+––––––––––-+––––––––––––+––––––––––-+––––––––––-+

The size of the eggs varies considerably, from 26 by 17 to 30 by 16 millimeters; sometimes they are perfectly round, 17 mm. in diameter.

_Ch. concinna._–The specific character by which this Terrapin may be easily recognised is a pair of orange-red broad streaks, which extend from above the eye to the sides of the neck. The general colour is olive-brown above, variegated with yellowish dark-edged lines, which, together with numerous rugosities, radiate from the middle field of each shield. The plastron is yellow, often with blackish symmetrical patches, and sometimes these become confluent and preponderant. Very young specimens are extremely pretty, the ground-colour of the carapace being green, each shield with darker, somewhat concentric markings, most conspicuous and regular on the upper surface of the marginals, where the marks of the adjoining shields form one pattern-system across the dividing lines. The plastron is either uniform yellow or has a few pairs of blackish spots {350}which stand so closely together that they form almost median patches.

The carapace is rough. The horny shields become very thin with age. The anterior margin of the small nuchal and the neighbouring marginals is faintly serrated. The posterior marginals form slight notches or indentations between their edges. The plastron is almost square behind. The edges of the jaws are nearly smooth, without hook and receiving-notch. The tail is short.

[Illustration: FIG. 77.–_Chrysemys concinna_, in its third summer, × 1.]

[Illustration: FIG. 78.–_Chrysemys concinna_, in its third summer, × 1.]

This species inhabits the South-Eastern States of North America, from Missouri and North Carolina to the Gulf of Mexico. Very large female specimens have a shell sixteen inches in length. The eggs measure from 33 by 25 to 39 by 25 mm. or about 1½ inch in the long diameter.

_Emys._–The plastron is movably united to the carapace by ligament, and in the adult has a slightly flexible hinge across the middle, between the hyo- and hypo-plastral plates and the pectoral and abdominal shields. The plastron is large, but does not quite close the box. Besides the small nuchal there are twelve pairs {351}of marginal shields. The head is covered with smooth skin; the temporal arch is complete. The limbs are extensively webbed. The tail of the very young is nearly as long as the shell, but it becomes relatively shorter with age, being reduced in the males to about two-thirds, in the females to half the length of the shell. Only two species are found in Europe, the other, _E. blandingi_, in Canada and north-eastern U.S.A.

_E. orbicularis_ s. _europaea_ s. _lutaria_, the European Pond-tortoise.–The shape and coloration of the shell change likewise much with age. In the very young the shell is round, and the shields are rough and slightly keeled, uniform dark brown above, black below, with a yellow spot on each marginal and plastral shield. When half grown the dorsal shields become quite smooth, and are striated or spotted, with yellow upon a dark ground. The head, limbs, and tail are dark, with yellow or light brown spots and small dots. In very old specimens all these yellow marks disappear on the shell, which then becomes uniform brown or almost black. The coloration is subject to much local and individual variation, and there are two main types, the spotted and the radiate. It is difficult to say which of the two is the prettier. One male which I caught in the Alemtejo was very beautiful. The shell was almost black with a greenish shine when in the water, and had many bright yellow and whitish spots. In the radiate type the yellow is sometimes preponderant, so that each shield becomes a study of delicately painted yellow, brown, and blackish lines radiating from the centre. This variety seems to prevail in the south of Spain, decidedly so in the Marismas, also in Northern Italy, whence most of the European markets are supplied. The largest shell in the British Museum is 19 cm. = 7½ inches long. Fischer Sigwart received one from Naples which was about 9 inches long, and this seems to have been kept as a pet, since its shell had been gilt. Specimens about 5 inches in length may be considered as fully adult. There are very few reliable observations on the growth of individuals. One of F. Sigwart's grew in eleven years only about 2.5 cm. = 1 inch, when its shell was 13.4 cm. = 5¼ inches long–total weight of the tortoise 491 grammes, about 1 lb. One of my own grew from 11 to 13.2 cm. shell-length, and 8.3 to 10.6 cm. in width within eight years, but this was one of the specimens which, living in a greenhouse, {352}did not hibernate. This European pond-tortoise is now restricted to Southern and Middle Europe, extending eastwards towards St. Petersburg and into Asia Minor, southwards into Algeria. Formerly it had a much wider range, having been found in post-glacial deposits in Southern Sweden, Denmark, the Netherlands, and in East Anglia. Specimens have been found in the peat of the fens of Norfolk and Cambridgeshire, contemporary with bones of the Beaver, Roe-deer, and Pelican. The same applies to North Germany, where its gradual disappearance from the western and central parts is obvious. Except in Central France it is now practically unknown to the west of the Elbe river. The country between the Elbe and Oder is now debatable ground, _Emys_ being exceedingly rare. Some fifty years ago this seems to have been different, to judge from the fact that farmers were rather fond of keeping a tortoise in the water-troughs of the cattle to keep the water free from worms and other impurities. Hence arose a silly superstitious custom. It was considered equally conducive to the health of the pigs to keep a tortoise in the foul tub into which all the dish-water and kitchen-refuse–as potato-peels, sour milk, etc.,–were collected before the mess was given to the pigs.

A specimen is still occasionally caught in the Havel and Spree rivers. I myself have heard of one or two in the backwaters of the Oder near Frankfurt, but they are vanishing, and it is difficult to say exactly why. The universal lowering of the water-level owing to better drainage cannot quite account for it, since there are thousands of suitable ponds, swamps, and backwaters left. In Poland and in Eastern Prussia the tortoise is still common.

This creature lives on a strictly animal diet. Worms, insects, frogs, fishes form its main sustenance. Fishes are regularly stalked. The tortoise watches its opportunity, slowly it half crawls, half swims along the bottom, rises imperceptibly by a few gentle movements of the widely spread-out webbed feet, then opens its sharp cutting jaws wide, and makes a grab at the belly of the fish. Frogs are most easily stalked when they sit upon a floating leaf. The tortoise rises from below, and often waits with the nostrils and eyes just above the water and close to the frog. After a while it sinks, and rises again, this time actually touching the toes of the non-suspecting frog, smelling at them and deliberately biting with a sideward turn of the head.

{353}[Illustration: FIG. 79.–_Emys orbicularis_, European Pond-tortoise (left), and _Clemmys leprosa_, Iberian Water-tortoise (right). × ½.]

{354}What the jaws have got hold of is not allowed to escape again. The tortoise holds on and tears the prey to pieces with the sharp-clawed fingers. This takes a long time, only the scraped-off flesh and the intestines being eaten. The skeleton remains and sinks to the bottom, while in the case of a fish, the air-bladder floats away on the surface, and remains there as one of the surest signs of the existence of tortoises in that locality. The bones are cleaned with wonderful neatness. Some of my grass-snakes shared this fate, their backbones, with the hundreds of pairs of ribs, being picked or rather scraped clean, scarcely less well than if they had been prepared for a museum.

As a rule the prey must be in motion to be seized, unless the tortoise has watched it before, and even then the latter prefers to smell it before biting. In captivity they soon learn to eat meat, and they become very tame, but in their native haunts they are extremely shy and cautious. Fond of basking upon a stone or on the banks, with the four limbs sprawling, or with the hind-limbs stretched backwards, and with the webs spread out so as to offer as large a surface as possible to the rays of the sun, they lie motionless for hours and appear fast asleep. But the slightest noise, or any other sign of our approach, is sufficient to send them plumping into the water, and to make them scuttle along with unsuspected agility. Nothing but the audible plump of the flat body and the widening rings of the disturbed water indicate their presence. After a long time of waiting we give it up, and turn away. That very instant we see a little ripple, caused by the withdrawing of the tortoise, which had come to the surface and had been watching us, with only the nose and eyes peeping out of the water, the rest being concealed between the floating vegetation. Apparently they cannot see us well with their eyes still under water, owing to the difference of refraction, otherwise they would not peep out and then at once turn back. It is certainly not for the want of air, since they can remain below for many hours without breathing.

Although they generally feed in the water, they come on land when tame and hungry enough to take the offered food. Sometimes they make long migrations, perhaps because their old home is dried up or does not yield food enough. They hibernate during the cold season, buried in the mud, and they do not appear until {355}the spring is well advanced. During the pairing season, on warm spring nights, they emit short piping sounds, and when they have found each other, the couple swim about together. The white, hard-shelled, long, oval eggs, averaging 25 to 15 mm., and about ten in number, are laid on land. This is a very laborious and curious business. The female having selected a suitable spot, not loose sand, but rather hard soil free from grass and other dense vegetation, prepares the ground by moistening it from the bladder and the anal water-sacs. Then it stiffens the tail and bores a hole with it, moving the tail but not the body. The hind-limbs then scoop out the hole, the broad feet moving alternately and heaping up the soil on the side, until the hole is about five inches deep, that is as far as the hind legs will reach. The eggs are laid at the bottom in one layer, divided and distributed by the feet. Lastly, the soil is put in again, and the tortoise, by repeatedly raising its body and falling down, stamps the soil firm and flat, roughens the surface a little with its claws, and leaves the nest to its fate. Nothing but an accident leads to its discovery. The young are hatched, according to locality and the kind of season, either in the same autumn or not until the next spring. Eggs laid in a garden at Kieff, in Russia, were hatched eleven months later. This implies hibernation of the embryo within the egg, and this is probably the usual course of events, resembling the conditions of the development of _Sphenodon_ (cf. p. 299). The pretty little creatures, scarcely larger than a shilling-piece, are exceedingly difficult to rear. They require a tank with green vegetation, stones to bask on and to hide under, and also dry ground and moss for a change. They eat flies, tiny worms, tadpoles, etc., greedily enough, but for some occult reasons they do less well than many another kind of water-tortoise. Miss Durham has, however, succeeded in rearing one, which is now in its fourth year; the shell is 2 inches long, and each shield shows three annual rings around the areola. This specimen spent the winters in an unheated room under moss, not in the water.

_E. blandingi_, the North American species, has a more elongated and decidedly higher carapace than its smaller European relation. The carapace is dull black with many pale yellowish spots; the plastron is yellow, with a large dark patch on the outer and hinder corner of each shield. The head is dark brown above, bright {356}yellow below and on the throat, a contrast which gives this tortoise a striking appearance. This species is extremely voracious, becomes easily tame, and spends a great part of the day on land, hiding under grass to avoid great heat, and withdrawing into the water for the night.

_Clemmys._–The plastron is immovably united with the carapace, and is devoid of any transverse hinge. The skull has a complete bony temporal arch. This genus, consisting of eight species, is otherwise very much like _Emys_, and is truly Periarctic.

[Illustration: FIG. 80.–Skull of _Clemmys leprosa_. × 3/2. _A_, dorsal view; _B_, from the left side; _F_, frontal; _J_, jugal; _M_, maxillary; _Par_, parietal; _Pr.f_, prefrontal; _Pt.f_, postfrontal; _Q_, quadrate; _Qj_, quadrato-jugal; _Sq_, squamosal.]

_C. leprosa_ s. _sigris_ (Fig. 79).–The upper jaw has a median notch for the reception of the upturned point of the lower jaw; the cutting edges of the powerful beak are smooth. The shell is flat and long-oval, nowhere serrated. The plastron does not quite fill the box. In the young the shell is nearly round, and the horny shields form three series of keels, of which the lateral pair disappear early; the shields are olive-brown, each with an orange spot or streak; the plastron is dark brown, with a yellowish margin. The adult looks very different. The shell has become much more oval, with the greatest width behind the bridge. The long shields are smooth, and in elderly specimens are without any trace of the original connective rings of growth. The general colour of the shell is uniform pale olive-grey, inclining to yellow on the plastron. The ground-colour of the soft parts is olive-grey, but the sides of the head are adorned with orange-red or yellow marks, the patch between the eye and ear and three or {357}four stripes on the neck being especially conspicuous. The limbs have pale yellowish streaks. All these markings are, however, subject to much individual variation. While, for instance, the half-grown creatures are distinctly agreeably coloured, often with a rich brown, nicely sculptured shell, and with conspicuous orange and yellow marks on the skin, the very old ones become rather ugly, the prevailing colour varying more and more into dull uniform pale olive-grey.

The "Iberian Water-tortoise" is typical of the Iberian Peninsula, and extends through Morocco and Algeria far into North-Western Africa. Unknown to the north of the Cantabrian range, decidedly scarcer than its cousin _Emys_ in the northern half of the Peninsula, it becomes common in the south. In the Alemtejo, in the lower parts of Andalucia and in Morocco, there is scarcely a pool, stream, or river in which it is not found, feeding on any living thing it can master, although fishes and frogs are its principal prey. When the streams and watercourses run dry, during the hot and dry season, the tortoises crowd together into the remaining pools, which soon become stagnant and filthy. But even these havens of refuge are not of lasting avail. They are soon cleared of anything edible, and the stinking water becomes dirtier and hotter day by day. Ultimately the tortoises leave the pool to hide under ledges of rocks, where they aestivate for months. This life in the muddy, slimy pools renders these tortoises peculiarly liable to the attacks of a certain fresh-water alga, which enters through the cracks in the horny shields and then flourishes in the Malpighian layer, and even in the underlying bone itself. This becomes gangrenous in patches, and the whole shell assumes a leprous appearance, hence the specific name of _leprosa_. Everything combines in favour of this destructive little alga. The tortoise, covered with mud, basks in the hot sun, the horny shields become brittle and crack, often peeling off in thin flakes. But those happy individuals which inhabit permanent rivers, or pools which do not dry up, are, and remain, as clean as other water-tortoises.

_C. leprosa_ has a most disagreeable, offensive smell, something like concentrated essence of fish, due to the secretion of a pair of large glands situated beneath the skin of the inguinal region, and opening behind the bridge. Freshly caught specimens stink horribly, but when they have become accustomed to being {358}handled, they no longer void these glands. They always withdraw into the water for the night, and the cold season is spent in the mud. Their time of propagation is still somewhat doubtful. Very young tortoises are met with in the Peninsula in March, when they are already in the rivers. Those which I imported in the summer and autumn invariably dug their nests and laid their long, oval eggs (28 to 33 mm. long) in the month of November, pairing having taken place some two or three months previously. The mode of making the nest is exactly the same as that described for _Emys_. As most of my specimens were kept in a greenhouse with a permanent current of warm water through their tanks, they never hibernated, nor did they pass through a torpid time in the summer, but they showed an irresistible love for the hot-water pipes, huddling together by the dozen, so that the pipes had to be screened off to prevent the creatures from getting burnt. Until this precaution was taken, they heated themselves so much that the shields and even the bones of the plastron were injured. The artificial warm temperature and the complete suppression of seasonal rest had no bad influence, most of the tortoises living with undiminished appetite for more than twelve years, but the sexual period became disturbed, pairing occurring ultimately at all times of the year. The eagerness of the males, however, had a peculiar evil secondary influence upon the females. The male tries to fasten on to its mate by biting into the collar-like fold of the neck into which the head is withdrawn, and this repeated irritation produces sores and swellings, which latter in their turn prevent the female from wiping the eyes with the back of the fore-limbs, a habit common to most, if not all, tortoises. Ultimately the eyes fester, and the tortoise, becoming practically blind, falls off its feed, leaves the water, which makes matters worse, and is very difficult to cure.

In other respects they are very hardy, and they stand acclimatisation in England perfectly. Some, thriving in a deep concreted pond, passed through the very severe winters of several years ago, hiding in the mud below the ice, and appeared in the spring in perfect health. They can also successfully pass the winter under moss and a heap of loose garden-rubbish.

_C. caspica_ is closely allied to _C. leprosa_, which it represents in the Balkan Peninsula and in Asia Minor. It differs from the south-western species chiefly by having the cutting edges of the {359}upper jaw finely denticulated, and by its prettier coloration, each shield being ornamented with yellowish streaks which form a kind of ∞ on the costals, and a ring on the marginals. The plastron is black in the young, with yellow and black patches in the adult. The head and sides of the neck are striped with yellow lines, narrowly edged with black, and the rest of the soft parts is marbled dark olive and yellow. A few other species occur in China, Japan, and North America.

_Clemmys insculpta_, one of the American species, ranging from Maine to Pennsylvania and New Jersey, is easily recognised by the peculiar reddish-brown and brick-dust colour of the soft parts. The strongly keeled, posteriorly emarginate carapace is reddish brown, with radiating yellow lines. Each shield is delicately sculptured. The plastron, which is notched behind, is yellow, with a large black patch on the outer corner of each shield. Length of a full-grown specimen 8 inches. They frequent the rivers and ponds, but are also very fond of leaving the water, sometimes remaining for months in dry places.

_Malacoclemmys_ of North America, with three species only, is closely allied to _Clemmys_, from which it differs chiefly by the very broad alveolar surface of the upper jaw, and by the more forward position of the entoplastron, this being placed anteriorly to the humero-pectoral suture. We mention this genus since one of its species, _M. terrapin_, is so extensively eaten in the Eastern United States. The shell is oval, slightly emarginate behind, obtusely carinated along the middle line. The upper parts of the shell are brown or greenish, with dark concentric lines; the marginals are yellow below, each with a ring of dark grey, and forming a peculiarly up-turned rim. The plastron is yellowish, either with concentric stripes and dusky lines or uniform yellow. But it is the colour of the soft parts which gives this otherwise dull-looking creature its delicately pretty appearance. The skin is, namely, greenish white with countless small black dots. The males remain much smaller than the females, and have the concentric stripes more pronounced. This species, the choicest of the edible Terrapins, frequents the salt marshes of the east coast of North America, from Rhode Island to the Gulf of Mexico, being most abundant around Charleston.

The following is a condensed account of an article which appeared in the New York Sun, 18th September 1898, the data {360}of which were supplied by the manager of the terrapin-farm at Beaulieu, Georgia. The continued hunting and the unfailing demand for them are making them very scarce, so that enterprising men have established terrapin-farms or "crawls" for the keeping and breeding of terrapins. The "crawls" in question are near the river. The larger is 310 by 60 feet, and is divided into three compartments for three sizes. The smaller "crawl" is for the babies, and is 100 by 8 feet. Through both "crawls" runs a ditch connected with the river and making a circuit of the farm. The bottom of the "crawls" is on a level with the low tide, and is covered with a layer of mud about six inches deep. Into this the terrapins burrow in the winter. The average population of terrapins is about 40,000, one half "bulls" and the other half "heifers." The latter are much better eating, and grow to a much larger size, namely, eight inches on the plastron, while the "bulls" rarely grow over five inches long. When a female reaches six to eight inches it is called a "count." Those between five-and-a-half to six inches long are known as "two-for-threes," while those from five to five-and-a-half inches are known as "halves." They are fed exclusively on shrimps and crabs on account of the flavour, although they will eat almost anything. The 40,000 consume on an average twenty bushels of crustaceans a day. They are quite indifferent to cold. The manager saw some placed in a block of ice and frozen fast to it; after four or five days they were chopped out, thawed, and were soon as lively as ever. The statement that it takes these terrapins only seven years to attain full commercial growth is surprising, and is probably an underestimate. At the end of the large "crawl" is a board to enable the females to creep into a sand-pit, where they lay the eggs from April to June, eight to twelve forming a set. It is necessary to get the babies away from their parents as soon as they hatch, else they will be eaten. The young must not be exposed to the cold. The old ones have a large amount of curiosity. The best way of catching them is for two men to go out in a boat with a net. They row carefully along until they come to a likely spot. Then one man raps several times sharply on the boat with a stick, and if there are any terrapin about they will come to the surface just as fast as they can get there to see what is going on, and the other man scoops them up with a little net. Another {361}way, used in the salt marshes, is for the negroes to go tramping through the mud and water. If they pass any terrapin these will rise out of the mud to see what the disturbance is. The captives are then fattened in the "crawl." When the men go in to feed them they whistle, and terrapin from all over the "crawl," thousands of them, come swimming through the water, piling over each other in their efforts to get close to the man with the shrimps and crabs.

_Cistudo._–The plastron, without forming a bridge, is connected with the carapace by ligaments, and is divided into two movable lobes, the transverse hinge being so perfect that the box can be completely closed after head, legs, and tail have been withdrawn. The nuchal shield is very small; the first four neurals are large and broad, the fifth much broader than long. There are twelve pairs of marginal shields. The carapace is high and arched. The digits are almost completely free. The tail is very short. The skull is without a bony temporal arch, the quadrato-jugal and the jugal being absent. Only two species, in North America.

_C. carolina_ of the Eastern United States is a very interesting species. Closely allied by its internal structure to the water-tortoises, it has become absolutely terrestrial; and the shape of the head, the convex shell which is coloured black and yellow or orange-brown, and the short webless fingers are all terrestrial features. But the rather long toes, provided with long and sharp claws, the broad and flat feet, enlarged by a broad fold of skin on the outer margin, the long oval eggs, the smooth covering of the head, and the preponderant animal diet, still proclaim the aquatic relationship of this tortoise. It is in fact a genus which has changed habits and features from aquatic to terrestrial life. The head is covered with a smooth skin, and the upper beak, especially in old specimens, is strongly and broadly hooked. The eyes of the males are red, those of the females are brown. The plastron of the males is concave, that of the females is flat. Large females reach a length of nearly six inches. The young are nearly round, with high, arched back and prominent keels. The keels of the middle line remain a long time, but they gradually flatten down with age, being prominent only at their posterior ends. Each dorsal shield is originally nicely sculptured, with a well-marked areola and concentric rings. Very old individuals {362}become much flatter on the top of the shell, but the sides remain steep, so that the whole shell roughly resembles a somewhat oblong box with the corners rounded off, and the whole upper surface rubbed down quite smooth. The variations of colour are almost endless, and they occur in the same localities. I have a number of all ages from Long Island, near New York. The half-grown are beautifully reddish or orange-brown with dark patches, median keels prominent, plastron uniform black-brown. In others the dark-brown prevails over the lighter markings, which are yellower and more spotted or dotted than patched. Some of the oldest, with quite smooth shells, are black, with small, round, light yellow spots. Others are vermiculated or striped with yellow and black. The soft parts vary to the same extent, some showing on the neck a beautiful intricate pattern of yellow, reddish and brown, while in others these colours are arranged more or less in longitudinal stripes.

These "Box-tortoises" are often caught in the States and kept as pets in the gardens, and their owners mark them by cutting their initials into the plastron. These marks heal up and widen in time like letters cut into the bark of a tree. One of my specimens, certainly a very old one to judge from his hooked beak, perfectly smooth and flat shell, and from the condition of the marginals, which have the edges rubbed down quite smooth and rounded off, has two initials and the date 1837 on its plastron. Of course there is no proof that the date had been cut in that year, more than sixty-three years ago, but it was done a long time ago. The scars on those parts of the shell which touch the ground are almost effaced, and the letters and figures have become somewhat distorted owing to the usual unequal, not concentrical, peripheral growth. Moreover, this tortoise must have been already adult, although not quite fully grown, since the marks are large and were evidently put in such a size and position as to fit the available space. I may mention that this record tortoise was, when I got it, not kept in confinement, but had been picked up at large.

These Box-tortoises become very tame. Although fond of drinking quantities of water in long and slowly repeated draughts, they do not go into the water, and if they fall in accidentally they are liable to get drowned. They enjoy a mixed diet, but animal food predominates, consisting chiefly of snails, the shells of {363}which are passed, slugs, earthworms, maggots, and soft caterpillars. Their fondness for slugs is all the more remarkable since scarcely any other Vertebrate eats these slimy, sticky molluscs; but a Box-tortoise will make a meal of two or more fat specimens of the black slug _Arion_, and it will eat dozens of small slugs. It first deliberately smells the prey, turns the head sidewards and gives a bite, whereupon first the intestines and then the rest are eaten. The slime is later on scraped off with the fore-limbs, or the head is rubbed against the grass. The favourite time of feeding is towards dusk or in the early dewy morning, and they are especially lively during a soft, warm rain. They also relish various kinds of fungi and fruit, for instance half-rotten bananas. Close observation of their habits gives us indications as to how the change from carnivorous to herbivorous habits may have taken place. Accidentally many a blade of grass is bitten off and swallowed together with the molluscs, also bits of rotten wood and moss, and their excrements are often full of such more or less digested matter. They are not very fond of basking, although they love warmth, creeping into the grass, where they make a shallow form by moving the shell backwards and forwards. During the cooler nights they frequently retire into a hole or under a log of wood. They require to hibernate. If kept in a warm house they become restless in the autumn, refuse food, drink and feed again after some weeks, but are liable to die during the winter. If they can find a cool place they bury themselves and sleep for several months. If left out of doors they dig into the ground, creep into a hole, at the bottom of which they half bury themselves, or they hide under a heap of garden-rubbish well out of the reach of frost. Warm April days bring them out, and the first requirement is a drink.

When walking about in search of food they assume a curious attitude, with the shell well above the ground, the long neck stretched out and raised high. Their temper varies individually. Some become tame readily and lose all shyness, and creep up to their friend to take food from his fingers. Others are decidedly shy and sulky, withdrawing with a hiss into the shell, which in some specimens shuts almost hermetically all round, and they do not come out until all imaginary danger is past. One of my males sulked thus for several months, at least we never saw anything of it except the closed shell, but it did not starve itself. {364}Propagation takes place in the summer, the long oval hard-shelled eggs being laid in June and July.

The TYPICAL LAND-TORTOISES are easily recognised by their feet. The digits are short, have not more than two joints, and are without any trace of webs; the metacarpals are scarcely longer than broad. The hind-feet are club-footed. The skin on the anterior side of the fore-limbs is covered with strong horny scales, frequently with dermal ossifications. The plastron is united suturally by a broad bridge with the usually strongly arched carapace. The skull has complete postorbital and temporal arches. The top of the head is covered with shields. The tail is short. There are only a few recent genera, modifications of the central and typical genus _Testudo_. The latter is cosmopolitan in the warmer temperate and tropical regions, except in the Australian and Austro-Malayan countries.

_Cinyxis_ (Fig. 82) with a few species in Tropical Africa from the Gambia and from Abyssinia to the Equator is remarkable for the unique modification of its carapace, the posterior portion of which is movable, the hinge passing between the seventh and eighth marginal and the fourth and fifth costal plates, externally behind the seventh marginal and the second costal shields. In the middle of the back the hinge is imperfect, the parts being merely flexible enough to permit the posterior half of the box to be closed. The head is covered with shields.

[Illustration: FIG. 81.–Skull of _Testudo nigrita_ s. _elephantopus_, from the Galapagos Islands. × ½. _M_, maxillary; _Op_, Opisthotic; _Pr.f_, prefrontal; _Pr.o_, prootic; _Pt.f_, postfrontal; _Q_, quadrate; _S.o_, supra-occipital.]

_C. belliana_, of Northern Tropical Africa, has a small nuchal shield, and the margin of the carapace is smooth. Length of shell up to seven or eight inches. _C. homeana_, of West Africa, has likewise a small nuchal shield, but the posterior portion of the carapace descends vertically, and the marginals are strongly reverted and serrated. _C. erosa_ (Fig. 82), also from West Africa, has no nuchal shield; the marginals are reverted and serrated, but the posterior part of the carapace is sloping, and the anterior {365}portion of the plastron is strongly forked in front, and projects beyond the anterior border of the carapace. This peculiar creature reaches a length of nine inches. When withdrawn within the shell, which is closed behind and depressed in front, with the jagged edges of the plastron and the anterior marginals protecting the drawn-in head, it has a very quaint appearance. It lives entirely on fruit and other vegetable matter, and is said to prefer to lie in the water, while _C. belliana_ is supposed to be entirely terrestrial.

[Illustration: FIG. 82.–_Cinyxis erosa._ × ½.]

_Pyxis arachnoides_, of Madagascar, a small land-tortoise, only four inches in length, has an immovable carapace, but the front lobe of the plastron is hinged.

_Testudo._–The plastron is immovable, except that in old individuals of some species, e.g. _T. ibera_, the hinder lobe develops a transverse flexible hinge. They have existed since the Oligocene of North America and Europe; and are now represented by nearly forty species in all the tropical and warmer temperate countries excepting the Austro-Malayan and Australian region. Typically terrestrial, herbivorous and frugivorous, although occasionally varying their diet with worms, molluscs, and insects. The eggs are hard-shelled, mostly less oval than those of the aquatic and semi-aquatic tortoises. The males generally remain smaller than the females, have a slightly longer tail, and have a concave instead of a flat plastron. Most land-tortoises hibernate in the ground during the cool and cold seasons, or they aestivate during the hot and dry months of tropical countries, but this is not an invariable rule.

_T. graeca_, the common "Greek Tortoise." The shell is very convex, without keels, and has a smooth, not serrated margin. {366}The nuchal shield is narrow. The fifth or last neural shield is much broader than the others. The supracaudal is usually divided in the median line, so that this is really the last pair of marginals. The plastron is notched behind; the axillary and inguinal shields are small. The scales on the anterior surface of the fore-limbs are small, and form from half-a-dozen to ten longitudinal rows. The hinder surface of the thigh is quite smooth. The tip of the tail ends in a conical, horny spur. The coloration of the shell varies somewhat, but the ground-colour is yellow, each shield with a dark brown centre and irregular patches or confluent spots towards the margin. The plastron has an irregular, broad black border. The soft parts are grey-yellowish. Some specimens are rather pale, almost lemon yellow with little black; others incline towards orange with more or less black. The middle fields of the shields of young specimens are granular, although this area is rubbed smooth with age; but the rest shows clearly marked concentric lines of growth. The eyes are dark, with a brown or bluish tinge, sometimes inclining to dark grey in very old specimens.

Full-grown females have a shell six inches in length. This species inhabits the northern half of the Balkan Peninsula, parts of Asia Minor and Syria, Italy, and most of the islands of the Mediterranean, from the Grecian Archipelago to the Balearic Islands.

_T. ibera_ is closely allied to _T. graeca_, from which it differs chiefly in the following points. The last pair of marginal shields are fused into an unpaired supracaudal, the median line of division being almost obliterated. The fifth neural shield is not broader, and generally a little narrower than the others. The posterior lobe of the plastron develops with age a transverse ligamentous hinge, and is thus rendered slightly movable, especially in the females. The posterior margin of the carapace is slightly expanded in old specimens. The scales of the fore-limb are large and imbricating, and form only four or five longitudinal rows. On the middle of the exposed posterior surface of the thighs the skin carries a strong, conical, horny tubercle. The coloration is much like that of _T. graeca_, except that the yellow of the young inclines to pale olive. Some specimens are uniform brownish. This species reaches a much larger size than _T. graeca_, old females often measuring eight inches, {367}rarely more than nine inches in length. Its home is Morocco and Asia Minor, extending into Persia. It also occurs in certain parts of Southern Andalucia, where it breeds regularly, for instance, in the sandy pine-forests of the Marismas, near the mouth of the Guadalquivir. Whether it has been introduced from Morocco, or is indigenous, is an open question. Its specific name refers to its Iberian home.

_T. marginata_ is worth mentioning, since it is the Greek tortoise, although not that of the European markets, which are supplied by the other two species. _T. marginata_ is restricted to Greece proper, where it is the only land-tortoise. It is less closely allied to _T. graeca_ than to _T. ibera_, of which it may be called an exaggerated form. The posterior margin of the carapace is much expanded or flanged, and serrated. The supracaudal is undivided, the posterior lobe of the plastron is movable, but the large conical spur on the thighs is absent. The dorsal shields of adult specimens are black with a small yellowish patch; the ventral shields are yellowish, each with a large black triangular patch. The British Museum possesses a shell 28 cm. = 11 inches in length.

The habits of these Moorish and Greek tortoises are very much alike, and since they enjoy the distinction of frequently being kept as pets in gardens, where they are allowed to look after themselves, a great many incidental and odd observations have been made on them. They are essentially vegetable feeders, but their taste varies individually and with the season, also according to the vegetation of the country they happen to come from. Most of them enjoy juicy plants, for instance, lettuce and cabbage; the flowers of the dandelion attract them not merely by their bright colour; clover is also a favourite food, and an enclosure of grass-land with clover in it is soon cleared of the latter; grass is also taken, in default of anything better. Some of my specimens gradually bite large holes into gourds and pumpkins; and in Morocco I found them in the autumn feeding entirely on the terribly astringent green fruits of the dwarf palm _Chamaerops humilis_. The larger specimens bolted the fruit with the stones, passing the latter. In close captivity they often learn to take and to like bread soaked in milk or water. They drink slowly and at length, but scarcely ever when they have succulent food. There is one thing which they do {368}not eat, namely, "black beetles," although they are warranted to do so by the men who hawk them in the streets. Worms, slugs, etc. are often mentioned as part of their occasional diet, but I am not aware that any of the hundreds which I have watched have taken such creatures, in spite of every opportunity. Their habits are very regular. They learn to know the geography of their domain thoroughly, and the spot selected for sleeping will be resorted to over and over again, be it underneath some broad leaves, under a bushy fir-tree, between a cluster of wallflowers, or between some tussocks, or even in an almost bare corner, the attractions of which are not at all obvious. Although their mental capacities cannot possibly be called brilliant, they soon learn to distinguish between different persons, and they will come up to be fed; but their memory for localities is surprising. Here is only one instance. A tortoise which had been put into an outhouse for hibernation was six months later taken to its usual large enclosure, and in the afternoon it tucked itself away on the top of a mound under precisely the same low bush where it used to sleep during the previous autumn. It could not see that spot from where it had been put down, and it did not meander about during the day, but after having enjoyed the warm sun it made straight for its favourite place. Dr. Girtanner of St. Gallen in Switzerland testifies to their appreciation of music. When the town-band began to play on the square adjoining his garden, all his tortoises crept as fast as possible towards the fence and remained there motionless with heads and necks erect. When the piece was finished they moved about, but when the next number began they were again spellbound. This he has observed, not on one but on many occasions. That they can hear, although their ears are not visible, but covered by the ordinary skin, is obvious enough from the fact that during the pairing season they emit feeble piping sounds.

They are extremely fond of basking in the hot sun, sometimes allowing themselves to be almost baked in it, but then again at other times they seem to be anxious to seek the shade. They rise late and go to bed early, being absolutely diurnal. In the summer they leave their quarters when the sun is well up, making for a sunny spot to graze. Then they lie still and bask, unless a shower causes them to retreat under shelter. {369}After some hours' rest they feed again, and in the afternoon, long before sunset, they go to bed. Some winters in England are of course much more severe than any which these tortoises experience in their native countries. Still they manage to survive them, provided they find a place which they can burrow into, deep enough to be out of the reach of frost; and if there is a heap of mould, rotting weeds, and leaves, they are probably safe. Sometimes they are restless, coming out again in unusually mild winters without, however, taking food. If they appear too early in the spring, they run the risk of terrible colds on prolonged wet and cold days, but in the autumn they are hardier, and can stand several degrees of dry frost.

The pairing season begins in May, but lasts far into the summer. In Morocco I found them pairing as late as the month of September. The preliminaries extend over many days. The male becomes unusually active, makes a piping sound, runs after the female, draws in its head, and knocks with its shell against that of the female. This is repeated many times, until the female is excited enough to raise itself upon its hind-limbs. The eggs, only two to four in number, are laid several weeks later, and are buried in the ground. They are roundish-oval, hard-shelled, and vary according to the size of the female. Those of _T. graeca_ measure on the average 30 by 24 mm.; those of a large specimen of _T. ibera_ 32 to 36 by 30 mm. The newly-hatched little creatures are still quite flexible, and apparently soon bury themselves before beginning their active life in the ensuing spring.

The age which these tortoises can reach is quite unknown, but there are reliable data of individuals having been kept for many years. Rumpf[133] kept two _T. graeca_ in his garden at Frankfort-on-the-Main, and let them hibernate in a box with hay in the cellar. One lived 33, the other 23 years. The most famous specimen of _T. ibera_ is "Gilbert White's Tortoise,"[134] which had been kept for more than 40 years before it came into his possession. It used to bury itself in November and to come out in April. It died in 1794, having reached an age of fifty-four _plus_ an unknown number of years, since there is no record of its size when it came to England. The same applies to every other specimen which has been, and is being, observed as a pet. My {370}largest Morocco female, which has a shell 7 inches long, shows at least 25 concentric rings of growth on the shields; the last half-dozen rings are very narrow, while some of those of the central area have been rubbed down. This creature is not improbably 30 years old. A small female, which is only 5¼ inches long, has already 14 rings on its still perfect shields. Lastly, a little one, only 4 inches long, shows 7 rings. They grow fastest when they are about 6 to 7 inches long, and they then seem to be at their prime. White's tortoise, now enshrined in the National Collection, was unusually large, the shell measuring 25 cm., or nearly 10 inches; around the much-enlarged, rubbed-down areola of each shield are about 30 very narrow rings.

_T. horsfieldi_ is easily recognised by its possessing only four claws on the fore- and hind-limbs. It is closely allied to the species last mentioned, which it seems to represent in the sandy districts of Transcaspia and the Kirghiz Steppes to Afghanistan.

_T. elegans_, the "Starred Tortoise" of the southern half of India and Ceylon, is easily recognised by the very convex carapace without a nuchal shield, and by the beautiful markings of the other shields, each of which has a yellow areola, whence radiate yellow streaks upon a black ground. Moreover, the dorsal shields often form humps. It reaches the length of one foot. Old specimens lose the beautiful yellow radiation, owing to a considerable amount of peeling off of the horny layers.

The habits have been carefully watched by Captain Thomas Hutton,[135] who gives the following account. The tortoises live in the grassy jungle at the base of the hills, but owing to their colour being so blended with the rocky nature of the ground, they are with difficulty distinguished. Moreover, they remain concealed beneath shrubs or grass during the heat of the day. In the rainy season they are most active, wandering about all day, feeding and pairing. At the approach of the cold weather they select a sheltered spot and conceal themselves by thrusting their shell into some thick tuft of grass, remaining there in a sort of lethargic, but not torpid, inactivity until the hot season, at which time they remain concealed only during the heat of the day, coming out about sunset to feed.

During the hot season Hutton's captives often soaked themselves {371}in water, and they drank a great deal. Copulation lasted about ten minutes; the females received the males from the end of June to the middle of October. On the 11th of November a female dug a pit at the root of a tuft of grass, having previously watered the spot, then digging with the hind-limbs alternately, and continuing to water the soil. In two hours she had made a hole six inches deep and four wide; she then laid four pure white eggs, each about 1¾ inches or 45 mm. long, and filled the hole again with the prepared mud, pressing it well in with the feet and with the weight of the body. The whole operation took four hours. From December to the beginning of February these tortoises were listless, they then took water and some lucerne, but did not come out again until the middle of April, well in the hot season. Both males and females wrestled in a curious way. One confronted the other, with the head and fore-limbs drawn into the shell, and with the hind-limbs planted firmly on the ground, and in this manner shoving against each other in any narrow space. Sometimes, if one succeeded in placing its shell beneath the other, he tilted his adversary over on his back, from which position he had great difficulty in recovering himself.

_T. polyphemus_, the "Gopher Tortoise" of the south-eastern States of North America, is one of the few American species. It is characterised by the shape of the front lobe of the plastron, which is bent upwards, and extends beyond the carapace. The nuchal shield is present, not narrow; the supracaudal is undivided. The shell is much depressed, and flattened along the vertebral region, with rounded margins. The fore-limbs are armed with very strong claws. The general colour is very dark brown above, inclining to black; brownish yellow below, with blackish patches. The length of the shell is about one foot, or even eighteen inches.

The Gopher is interesting for its habits, which are described by Agassiz, Schnee, and others. Its domicile consists of an excavation, the mouth of which is just sufficient to admit the animal, the burrow running in an oblique direction to the depth of about four feet. The whole passage is sometimes more than two yards long. It expands from the entrance, and ends in a roomy space, sometimes with a few branches of fir trees which have been dragged in either for food or as a lining. The burrow {372}is inhabited by one pair only. When the dew is on the grass, or after rain, they emerge in search of food, which consists of grass, succulent vegetables, fruit, etc. They also eat the gum that exudes from trees, especially the resin of the pine. The eggs are laid in June, not in their domicile, but in a separate cavity near the entrance; a set consists of five eggs, almost round, and very large, namely, 40 mm., or more than one inch and a half in diameter. To capture the Gopher a deep hole is dug at the mouth of their home, into which they fall as they emerge for food. In Southern Texas and neighbouring parts of Mexico they are represented by a smaller and lighter coloured species.

_T. tabulata_, widely spread over Tropical South America, whence it is often brought over as a curiosity, reaches a large size, specimens nearly two feet in length being not uncommon. The shell is flat on the top, and is very elongated, without a nuchal, but with an undivided supracaudal shield. The carapace is very dark brown or black, each shield with a yellow or orange centre; the plastron is brown and yellow, the dark colour being mostly confined to the middle portion. The ground-colour of the skin of the limbs is blackish, but the scales are orange or red. The head is yellow and black. This species inhabits the forests, and lives chiefly on the fruits of trees; in captivity they are said to take bread soaked in milk or water, lemons, apples, bananas, cabbage, gourds, and also meat, at least the males.

GIGANTIC LAND-TORTOISES differ from the others in no essential points except their large size. The term gigantic is, however, applied to many of them by courtesy only, since they do not exceed the dimensions of large Turtles. A truly gigantic species, _T. atlas_, has left its remains in the Sivalik Hills of late Miocene or early Pliocene date. The skull is between seven and eight inches long, and is well preserved, but the correctness of the dimensions of the specimen, as it now stands, restored in the National Collection, is open to doubt. The shell was probably not more than six feet long. Miocene and Pliocene Europe was also inhabited by large tortoises, with shells about four feet long, _e.g._ _T. perpigniana_, whose bony plates are one inch thick; others have been found in North America. Such large tortoises are now restricted to two widely separated regions of the world, namely the Galapagos Islands (which have received their name from these creatures, _galápago_ being one of the Spanish terms for {373}tortoise), and the islands in the Western Indian Ocean, namely the Mascarenes (Bourbon, Mauritius, and Rodriguez), the Comoros, Aldabra, the Amirantes, and the Seychelles. When they became extinct in Madagascar is not known, but _T. grandidieri_ was a very large species of apparently very recent date. Of the other islands the Comoros only were inhabited by man, the others were devoid of any but small and harmless Mammals. It was on these peaceful islands that large tortoises lived in incredible numbers, and, like the Dodo of Mauritius and the Solitaire of Rodriguez, grew to a size far beyond that of their less favourably placed continental relations. The same applies to the tortoises of the Galapagos Islands. Plenty of food, a congenial equable climate, and absence of enemies enabled them to enjoy existence to the fullest extent. There was nothing for them to do but to thrive, to feed, to propagate, to grow, and to vary. At least there was nothing to check variation within reasonable limits. Scattered over the many islands, they were prevented from inter-breeding, and thus it has come to pass that not only every group of islands, but in the case of the Galapagos almost every island, has or had its own particular kind, be these called varieties, races, forms, or species.

There are four features of special interest. First, these tortoises grow to a large size, and there are no small species on any of these islands. Secondly, they vary much individually. Thirdly, each island or group of islands has developed its own kind. Lastly, there is the widely spread tendency to reduce the thickness of the bony plates of the carapace, in spite of its size. In some cases, notably _T. vosmaeri_ of Rodriguez, the bony shell is reduced to apparently the utmost limit compatible with mechanical safety. The horny shields are, or were, however, well developed, sometimes much more so than in other recent land-tortoises. Whatever were the original reasons for the development of a strong shell in tortoises, they cannot have prevailed in these islands.

Where did all these tortoises come from, and how did they get to these oceanic islands? Accidental transport or migration are out of the question. Land-tortoises are drowned within a few hours. Moreover, there are none of their kind on the continents of Africa, Asia, and South America, although they had a much wider distribution in past geological ages. Consequently we have to assume that they are descendants of tortoises once populating the land which, except the islands, lies now below {374}the western Indian ocean. The existence of this, "Lemuria" or "Gondwana," came to an end in Mid-Tertiary times. The large tortoises on the remaining continents died out–in any case they are gone, while those which lived on, or retreated to, what became the present islands, survived and flourished.

The tortoises were not left in peace with the advent of man, who found that they were good to eat. They were first exterminated on the Mascarene Islands. In 1759 four small vessels were specially appointed for the service of bringing tortoises from Rodriguez to Mauritius; one vessel carried a cargo of 6000; and altogether more than 30,000 were imported into Mauritius within the space of eighteen months. Dr. Günther very properly remarks that many of these tortoises must have been small-sized specimens, and that many of them were probably used for provisioning passing Government vessels. Anyhow an inter-insular traffic was carried on, and there are records of superfluous tortoises having been turned loose, at the end of the voyage, in distant islands, even in Java. Importation and exchange of choice specimens, by way of presents, seems also to have taken place. All this makes it now actually impossible to trace the original habitat of the few surviving specimens with anything like certainty. At the beginning of this century the large tortoises had been nearly cleared off most of the islands, and at the present time only the south island of Aldabra enjoys the reputation of still possessing some really indigenous tortoises. The few survivors on the other islands are said to have been introduced. The small stock at Aldabra is now under Government protection. Representatives of various species will linger on for a little time to come, when they are kept as pets on some tropical islands, but those which have been brought to Europe are of course doomed.

We can mention only a few of the large tortoises which have become famous, not to say historical. A fascinating résumé of the whole complicated question has been given by Dr. Günther.[136]

_Testudo gigantea_ s. _elephantina_ s. _hololissa_ s. _ponderosa_, originally confined to the North Island of Aldabra, where this {375}kind has been completely exterminated, is now still to be found in the Seychelles in considerable numbers, introduced there by planters, and kept in a state of semi-domestication. A very large specimen was received by the Hon. Walter Rothschild, at Tring, in 1893. In 1897 its shell measured 40¼ inches in length, 52¼ over the curve, and 50 inches across the curve transversely; it weighed 358 lbs. The measurements taken in previous years are unfortunately not free from mistakes. "Whenever the temperature was over 60° F. this tortoise had a free run of 350 acres of grass park, and when the temperature showed permanently below 58°, it was kept in an orchid house from September to June. When at liberty in the park it lived entirely on grass, but in the hothouse it fed on carrots, cabbage, lettuce, and several other vegetables"; it was also very fond of rotten fruit. To this species belongs the large tortoise which has been living at St. Helena for more than the last hundred years.

_T. daudini_ is the species of the South Island of Aldabra. Voeltzkow, in 1895, succeeded in carrying off seven specimens. He gives the following description:–The island is an atoll, cut through in three places, with a greatest length of about twenty miles. The chief hindrance in the search for the tortoises is the impenetrability of the island. The soil consists entirely of sharp water-worn corals, with their points uppermost, while the whole is covered with such thick masses of low scrub, that a way has to be cut with an axe, so that an extended search over a large area is out of the question. To land on the outside is dangerous, on account of the heavy surf; while landing from the inside of the atoll is much hindered by the dense thickets of mangrove trees. As drinking water, and that very bad, is only found in one place, rainwater has to be collected from the natural hollows, and carried along in tanks. Thousands of mosquitoes prevent one remaining over night in those places which the tortoises frequent. Then at last, when one has discovered, by a stroke of luck, one of these creatures, in the thick scrub, where they hide during the heat of the day, the real hard work begins, namely, the conveyance of the beast. Six reached Europe alive, two of them were sent to Frankfort, and the four others to Hamburg. Mr. Rothschild received a male of _T. daudini_, which, until its recent death, was the largest living tortoise known. The length {376}of its shell was 55 inches, or 67½ inches over the curve; total weight 560 lbs. This specimen had a chequered career. Although its original home must have been the Aldabra atoll, it had been known for many years on Egmont Island, one of the Chagos Islands. According to tradition, it had been there some 150 years, but the first settlement on that island was formed from Mauritius only at the beginning of this century. The owner of the tortoise, M. Antelme, took it to Mauritius, whence it came to England. On the Egmont Island it used to bury itself for six months in the ground without eating anything.

[Illustration: FIG. 83.–_Testudo daudini_ (above) and _T. abingdoni_ (below). × 1/20.]

_T. sumeirei._–This kind is supposed to have been the species peculiar to the Seychelles. In 1766 five large tortoises were brought from the Seychelles to Mauritius by Chevalier Marion de Tresne. Of these only three were alive in 1898, two in {377}Mauritius and one in London; the latter specimen soon died in the Zoological Gardens. One of the two survivors, the last of their race, is famous. It was kept at Port Louis, and when Mauritius became a British possession in 1810, the tortoise was especially mentioned and taken over. It still lives there in the grounds of the barracks of the garrison. According to the proverbial oldest inhabitants it had in 1810 already reached its present size, namely, a shell-length of about 40 inches with a greatest circumference of 259 cm. = 8 feet 6 inches. Total weight 160 kilo = about 358 lbs. When walking it stands 63.5 cm. = 25.4 inches high, with the plastron about 15 cm. or 6 inches above the ground, and it can then carry with ease two full-grown men on its back. This old male is now nearly blind, but is otherwise of regular habits and in good health. Although it has been known for nearly 150 years it had to wait for its scientific name until the year 1892.

Another famous individual is the Colombo tortoise. It is supposed to have come to Colombo from the Seychelles in 1798. It died in 1897. To judge from photographs, this specimen, a male, may possibly belong to _T. sumeirei_, in spite of the very flat shell, which is 53½ inches in length.

Leaving aside the remains of sub-fossil tortoises, _e.g._ the thin-shelled _T. vosmaeri_ of Rodriguez, and several kinds which have been dug out in the Mare-aux-songes of Mauritius, one of which had a markedly forked and prolonged anterior plastral lobe, rather resembling that of the Pliocene Sivalik _T. atlas_, we now turn to the tortoises of the Galapagos Islands. They existed in enormous numbers towards the end of the seventeenth century, when Dampier visited those islands. Hundreds were exported and scattered early in the nineteenth century. When the islands became a penal settlement of Ecuador, the introduction of convicts and pigs proved detrimental to them, but Darwin found them still present in 1835 on most of the islands. His classical account of these old giants is to be found in the _Voyage of the Beagle_. They lived on the succulent cactus plants, leaves of trees, berries, and a kind of _Usnea_, a lichen pendant from the trees. They collected regularly at certain pools and springs, leading to which were regular well-trodden paths, formed by the coming and going of the tortoises. He calculated that they could walk a distance of about four miles in one day. During {378}the time of propagation the males emit a hoarse bark, which can be heard a hundred yards off. The round eggs measure about 5 cm. or 2 inches in diameter, and are laid in the month of October, about one dozen making a set.

Nearly every island had apparently its own kind. They are all remarkable for their small head and the length of their neck, which is decidedly longer and more slender than that of the Eastern tortoises. The most peculiar looking are or were _T. ephippium_ and _T. abingdoni_, the shell of which is extremely thin, with large lacunae in the osseous plates. The profile of the shell is somewhat saddle-shaped, with the horny shields

## partly concave and turned upwards at the sides. The general colour of these

and the other Galapagos tortoises is black. _T. ephippium_ still survives on Duncan Island. Of _T. elephantopus_ s. _vicina_ Baur collected twenty-one specimens in 1893 on Albemarle Island. Some of them are still comparatively young, only 16 inches long. A large one was killed, and, being hard up for water, Baur and his companions drank the five cups full of fluid contained in the pericardial sac; they found it most refreshing, and tasting somewhat like the white of an egg. One monster is said to have measured 56 inches over the curve, with a skull 7.12 inches in length. Mr. Rothschild received one of this kind alive–a much-travelled specimen. It came to England from Sydney, whether it had been brought in 1880 from Rotuma Island, north of the Fiji group. There it had probably been left with others by Captain Porter, who, on his voyage from the Galapagos in 1813, distributed several young tortoises from his stock among the chiefs, and permitted a great many to escape into the bushes and among the grass. The shell of this specimen measured 49½ inches in length, 56 over the curve.

FAM. 6. CHELONIDAE (_Turtles_).–The limbs are paddle-shaped, and the shell is covered with horny shields. Only two recent genera, with three species, widely distributed in the seas.

The neck is short and incompletely retractile. The temporal region of the skull is completely roofed over above and laterally by the parietals, postfrontals, squamosals, quadrato-jugals and jugals. All these bones are much expanded, and form the additional or false roof. The parietals are especially large, and are in broad contact with the squamosals. Nasals are absent. The nares are bordered by the small premaxillaries, the maxillaries, {379}and the prefrontals. The choanae are enclosed by the palatines, which are separated by the vomer, and are posteriorly in broad contact with the pterygoids. The latter are connected with descending processes of the parietals by epipterygoids. The foramen magnum is bounded not only by the supra-occipital and the lateral occipitals, but also by the basi-occipital. For the skeleton see Fig. 65, p. 320. The pubic and ischiadic symphyses are connected by a narrow cartilaginous band. The pubis has a large, broad, lateral process, but the ischium is devoid of such a process. The paddles of the fore- and hind-limbs are produced by an elongation of the metacarpal and metatarsal bones and of most of the phalanges, and these have no condyles; most of the carpal and tarsal elements are flattened, and additional width is given to the hands by the much enlarged pisiform bone. The number of phalanges of the five fingers is 2, 3, 3, 2, 2; that of the five toes, 2, 3, 3, 3, 2.

[Illustration: FIG. 84.–Skull of _Thalassochelys caretta_; cf. also Fig. 63, p. 317. _A_, Dorsal view; _B_, ventral view; _F_, frontal; _Jg_, jugal; _Mx_, maxillary; _Op_, opisthotic; _P_, parietal; _Pal_, palatine; _Pr.f_, prefrontal; _Pt.f_, postfrontal; _Ptg_, pterygoid; _Q_, quadrate; _Quadr_, articular surface of quadrate; _Qj_, quadrato-jugal; _S.o_, supra-occipital; _Sq_, squamosal.]

The carapace is heart-shaped and very flat. The nuchal plate has no rib-like processes. The eight neurals form a continuous series, and the short tail is covered by two or three pygal plates besides the unpaired last marginal. The number of all the {380}marginals is 23, sometimes 25 individually. The plastron (Fig. 66, p. 321) is composed of the usual nine plates, which, however, remain entirely free from the marginals, and are only loosely connected with each other, enclosing a very large unossified space. The horny shields covering the plastron number 13, and there is a series of about 5 inframarginals (Fig. 61, 6, p. 315). There are normally 12 pairs of marginal shields, a nuchal, 5 neural, and 5 or 7 costal shields. Whilst the number of these dorsal shields is pretty constant in _Chelone_, it is subject to an astonishing amount of individual variation in _Thalassochelys_.

The Chelonidae are a highly specialised offshoot of the Cryptodira adapted to marine life. Fundamentally they agree most with the Testudinidae, paradoxical as this may appear at first sight. There is nothing primitive about them except the complete series of inframarginal shields. Fossil forerunners of marine turtle-like creatures appear in the Upper Jurassic deposits of Europe and North America. The numerous genera have been grouped together as Thalassemydidae and Chelonemydidae. They are more or less intermediate between Chelonidae and _Emys_-like Testudinidae, the carapace being not too much flattened and broadened out, the fontanelles between the ribs are mostly small, the plastral bones are still broad, enclose a smaller ossified space, and there is still a bony bridge in most cases. The paddle-shape of the limbs is less pronounced, and sometimes only indicated. In some forms, especially _Lytoloma_, from the Upper Cretaceous and Eocene of North America and Europe, the anterior portion of the skull is much longer than in the Chelonidae, the vomer and the premaxillaries are elongated, and the anterior portion of the roof of the mouth, with the corresponding parts of the lower jaw, seems to have carried crushing pads. Some of the best-known Upper Jurassic genera are _Eurysternum_ and _Idiochelys_; _Plesiochelys_ from the Purbeck and Wealden; _Allopleuron hofmanni_ from the Upper Cretaceous of Belgium approaches _Chelone_ by the large fontanelles between the small marginal and the short costal plates. True Chelonidae are very rare and imperfect in the Mid-Tertiary strata, but both recent genera seem to have existed since Pliocene times.

The few recent Chelonidae are entirely marine, going on land only in order to deposit their eggs in the sands of unfrequented shores. Their distribution, in conformity with their oceanic life, {381}is almost cosmopolitan within the warmer zones, but not a few find their way far into the temperate seas. They are all eagerly hunted by man either for food or for the sake of the tortoiseshell.

_Chelone._–With only four pairs of costal shields. Carapace with large persisting fontanelles between the costal and marginal plates. Two species.

_Ch. mydas_ (the "Green or Edible Turtle"), has when adult a nearly smooth shell, all the shields being juxtaposed, fitting closely into each other, and becoming quite smooth with age. The neural shields of younger specimens have a feeble keel. The twenty-five shields which surround the carapace form a smooth, or but indistinctly serrated rim. The head is covered with one pair of prefrontal shields, the others are small. The horny beaks of the upper and lower jaws have denticulated outer edges, those of the upper jaw having two pairs of strong denticulated ridges. The limbs have generally only one claw, namely on the first digit. This claw, although sometimes curved and thick, and more than an inch in length, is blunt. The general colour is olive or brown above, with yellowish spots or blotches; the under parts are pale yellowish. This species attains a large size, with a length of shell of nearly four feet, but the usual length of full-grown specimens is three feet, and these weigh, when in good condition, more than three hundredweight. Their home is in the Atlantic, Indian, and Pacific Oceans, but there are certain regions in which they are more common than in others. Famous centres are the Island of Ascension, the West Indies, and the coast of Mosquito, at least for commercial purposes. As they require sandy, easily accessible beaches for the deposition of their eggs, they congregate in certain parts of the world more than in others, and being strictly vegetable feeders, they are naturally bound to the coasts, although they are sometimes met with far out at sea. Their chief food consists of algae, and of _Zostera marina_, the edible "Dulce," which grows plentifully in the lagoons of the coast of Florida. When they have eaten their fill, they are said to chop off more of these plants, and roll them, together with the adherent mud, into balls of the size of a head, and these balls, receding with the tide, are followed by the Turtles.

Whilst in the water they are caught in various ways, with {382}nets or harpoons. In some parts of the world the natives follow them in a boat, and when they espy a turtle crawling along the bottom, a man, attached to a rope, dives in, clasps it, and is brought up by his companions together with his prey. Turtles are fond of basking asleep, floating on the surface, and they are then harpooned from a stealthily approaching boat. The most original mode of catching them is that used by the natives of Torres Straits, Madagascar, and Cuba. The turtle-fishers go out in the boat to a spot frequented by grazing turtles; a long string is tied to the tail of a fish, _Echeneis_, a member of the Mackerel family, and the _Echeneis_, anxious to get away to protective shelter, makes for a turtle, and attaches itself to the turtle's plastron by means of the large sucking apparatus on the top of its head and neck-region. The men are guided by the string, and the turtle is gently coaxed up towards the surface or followed into shallow water, where it is either harpooned or dived for. It is curious that this use of the _Echeneis_ exists in such widely separated parts of the world, the natives of which cannot have any knowledge of each other. These modes of catching turtles are sportsman-like, but the greatest and most wanton destruction is practised at their breeding places. In conformity with the wide distribution of these creatures, the time of breeding is not the same everywhere. In the West Indian region, and in the Straits of Malacca, it falls within the period of April to June; on the coast of West Africa it occurs from September to January. The females come to their breeding places from afar, reconnoitre the beach carefully, are extremely wary and shy, taking alarm at the slightest disturbance, and at last crawl on land. Well out of the reach of the tide the female scoops out a hole in the sand, deposits about one hundred or more of its round, rather parchment-shelled eggs, covers the nest carefully, obliterating all traces of the dug-out sand, and makes again for the sea by another route. At least they are said to make a sort of circuitous route so that nobody can tell the position of the nest, which may be anywhere beneath the broad trail left by the heavy creature on its way from and back to the sea. The nest is discovered by probing the sand with sticks. The time of incubation is not known, but according to Agassiz, lasts at least seven weeks.

{383}[Illustration: FIG. 85.–Three turned Turtles, a Seal, and Albatrosses, Laysan Islands, north-west of the Sandwich Islands. From a photograph belonging to the Hon. W. Rothschild.]

{384}The "turning" of turtles is a cruel and wanton operation, since frequently many more are turned over and left to perish than are taken away. Men lying in ambush watch the beast, or they approach the lonely sandy shore by boat, and rush the helpless creatures when these are surprised in sufficient numbers. It takes several men to lift a full-grown specimen. It is therefore necessary to secure them by turning them over with poles or by their flippers, lest they should crawl away. On board ship they are either put into tanks or tied with ropes on deck, covered with a moistened cloth; and occasionally a piece of bread, soaked in sea-water, is thrust into the parched mouth. In London they are kept in large tanks, often in considerable numbers, but since they take no food in captivity, or rather because it is difficult to supply them with the right sort, they are not kept long. After the head has been cut off, the body is suspended for a day or two, in order to drain it of the blood. It is not only the meat and the fat which are used for the making of the famous soup, but also the thick and dense layer of subcutaneous tissue which lines the inside of the shell.

Tennent describes a revolting spectacle exhibited in the markets of Jaffna, in Ceylon. The flesh of the turtles is sold piecemeal by the Tamil fishermen, while the animals are still alive. At certain seasons, says the same authority, the flesh of turtle on the south-west coast of Ceylon is usually avoided as poisonous, but some lamentable instances are recorded of neglect of this, and consequent sickness, followed by coma and death. In the Gulf of Manaar specimens are frequently found between four and five feet in length; and on one occasion, in riding along the seashore north of Putlam, he saw a man in charge of some sheep, resting under the shade of a turtle shell, which he had erected on sticks to protect him from the sun. In connexion with this curious sight, Tennent quotes Aelian's statements, copied by him from Megasthenes' _Indica Frag._ lix. 31, that in the Indian ocean turtles occur which measure fifteen ells, so that not a few people may find ample shelter beneath a single shell.

_Ch. imbricata_ ("Hawksbill Turtle").–The number of shields covering the carapace is the same as in _Ch. mydas_, but they strongly imbricate, or overlap each other from before backwards, until the animal is very old, when the shields become juxtaposed.

{385}[Illustration: FIG. 86.–_Chelone imbricata_ ("Hawksbill Turtle"), young. × ½.]

In young specimens, under one foot in length, each of the neural and costal shields is strongly keeled, the three rows of keels converging towards the posterior end of the shell. The neural series of keels is almost continuous, and remains longest, even in half-grown specimens. The twelve pairs of marginal shields form at first a strongly serrated sharp edge; the serrations disappear gradually on the front portion, but remain on the posterior half of the shell. The horny covers of the jaws form a hooked beak, with sharp but smooth or feebly denticulated margins. The fore- and hind-flippers have two claws. The young are pale brown above, blackish below; the shell of the adult is beautifully marbled with yellow on a rich dark-brown ground; the plastron is yellow. The shields and scales of the head and limbs are dark brown, with yellow margins. The top of the head is covered by a large unpaired frontal and a pair of prefrontal or interorbital shields. This Turtle does not reach the size of the green or edible kind; the largest shell on record is in the National Collection, and measures 85 cm. = 34 inches in length. They range over all the tropical and subtropical seas. They are apparently strictly {386}carnivorous, living upon fish and molluscs, the shells of which they crunch. Although not eaten, they are much persecuted on account of their shells, the horny shields of which are the "tortoiseshell" of commerce. A large specimen yields up to 8 lbs. Few of the shields are, however, thick enough to be manufactured into the larger articles which art and fashion delight in, but if heated in oil, or boiled, they can be welded together under pressure, and be given any desired shape. In genuine articles of Oriental manufacture these welds can generally be detected, or their compound nature is indicated by the beautiful pattern, which is too regular in the imitations now common. Even the shavings and leavings can be welded and moulded into large pieces. The stripping of the shields has been described by Sir E. Tennent. "If taken from the animal after death and decomposition, the colour of the shell becomes clouded and milky, and hence the cruel expedient is resorted to of seizing the turtles as they repair to the shore to deposit their eggs, and suspending them over fires till heat makes the plates on the dorsal shields start from the bone of the carapace, after which the creature is permitted to escape to the water. At Celebes, where the finest tortoise-shell is exported to China, the natives kill the turtles by blows on the head, and immerse the shell in boiling water to detach the shields. Dry heat is only resorted to by the unskilful, who frequently destroy the tortoise-shell in the operation." The cruel process described above is resorted to "for economy's sake," the Singhalese believing that such maltreated turtles regenerate the shields, to be caught and shipped again. Since none of them are actually re-caught in the mutilated condition, this is looked upon as a proof of the correctness of the treatment. It is more likely that they die.

New shields can be reproduced only if the underlying Malpighian layer of cells (_cf._ Fig. 68, B, p. 323) is not killed by the roasting. However, Dr. Charles Hose, with his long experience in Borneo, is positive that numerous individuals are there caught which have imperfectly mended shells, the shields of which do not imbricate, are thin, and almost worthless.

It is commonly believed that the same individuals return again and again to the same spot for laying. This is very likely the case. Tennent mentions that in the year 1826 a Hawksbill was taken near Hambangtotte, which bore a ring attached to one of its fins, that had been placed there by a Dutch {387}officer thirty years before, with a view of establishing the fact of these recurring visits to the same beach. The same homing instinct has been observed in some females of the Green Turtle, which, having been brought from the Tortugas Keys to Key West off the south end of Florida, escaped, and were, a few days later, re-caught at the Tortugas. On the other hand, experiments made with turtles at Ascension are said to have had no result.

_Thalassochelys_, with five pairs of costal shields. The carapace is completely ossified in the adult, leaving no fontanelles between the ribs and the marginals.

_Th. caretta_ (the "Loggerhead Turtle").–The shields of the carapace imbricate only in young specimens, in the adult they become smooth and juxtaposed. The margin is serrated posteriorly. The carapace of the young has three strong keels. The intergular shield is very small or absent. The marginals, including the nuchal, usually number 23, rarely 25. The large head is armed with hooked jaws, the crushing surface of the horny upper beak has a median prominent ridge. The top of the head has a pair of shields in front of the unpaired frontal. The flippers of the young have claws on the first and second digits; in the adult usually only that of the first digit remains. The general colour of the shell is uniform brown above, yellowish below. Very young specimens are uniform dark brown or blackish above and below.

Large individuals have a shell about three feet and a half in length. The Loggerhead is carnivorous, and is commercially of no value. Its habits seem to be the same as those of the other Turtles, but it has a much wider distribution. Besides all the tropical and intertropical seas, it inhabits the Mediterranean, and is an accidental visitor to the western coasts of Europe, especially Portugal and the Bay of Biscay. It has been caught several times on the coast of Belgium, and an old female containing 1150 eggs was captured in 1894 on the Dutch coast. In 1861 one was caught near Penman, on the coast of Banffshire, and a second in the completely land-locked Loch Lomond.[137] It has been more frequently recorded from the coast of Devon and Cornwall.

The most interesting feature of the Loggerhead is the {388}astonishing variability in the number of the horny shields of the carapace. The normal number of shields of the carapace, leaving out the marginals and counting the nuchal as the first neural, is 6 neurals and 5 pairs of costals, in all 16. The greatest number of dorsal shields observed is 8 neurals and 8 pairs of costals, in all 24. Many of the intermediate combinations have been observed, there being, for instance, specimens with 8 neurals and 16, 14, 13, 12, or 11 costals, the latter not being always in pairs, but unequal on the right and left sides; or there are 7 neurals with 20 to 16 costals, or 6 neurals with 20, 19, 18, 17, or 16 costals. The interesting fact in connexion with these variations is, moreover, that some of the shields are much smaller than the others, sometimes mere vestiges in all stages of gradual suppression, and that the abnormalities are much more common in babies and small specimens than in adults. The importance of these "orthogenetic" variations has been discussed on p. 326.

SUB-ORDER 2. PLEURODIRA.–_Neck bending laterally and tucked away in the niche formed between the anterior portion of the carapace and plastron. Pelvis ankylosed to the shell, the broadened tops of the ilia to the carapace, the distal ends of the pubes and ischia to the plastron._

Freshwater tortoises, almost entirely carnivorous, inhabiting South America, Australia, Africa, and Madagascar. Fossil forms are known from the Jurassic epoch onwards.

Owing to the strong connexion of the iliac bones with the costal plates the sacrum has become practically abolished, the sacral ribs being reduced to one pair (the posterior of the original two pairs) or being absent. The centra of the cervical vertebrae articulate by cup and ball joints. The formation of the temporal region of the skull varies considerably in the three families, some genera lacking the complete zygomatic arch, while others have a narrow parieto-squamosal arch bridging over the temporal fossa, or the latter is completely roofed over by the laterally expanded parietal, which meets the jugal and quadrato-jugal. The quadrate is always trumpet-shaped; the rim of the tympanum is complete, but the posterior part of the trumpet remains open. The basisphenoid, pterygoids, and palatines form a broad and flat roof to the mouth. The vomer is large, and separates the palatines in the Chelydidae; it is very much {389}reduced or absent in the Pelomedusidae, in which the palatines meet. All the Chelydidae, except _Chelys_, have nasal bones which remain distinct from the prefrontals. The choanae lie in front of the palatines, divided by the vomer when this is present, but they are not roofed in ventrally.

The ilia are solidly ankylosed in the adult with the neighbouring costal plates, mostly with the last two pairs, sometimes also with the pygal plate. The lateral processes of the pubes fuse with the xiphiplastra. The ischia are also attached to the same plastral elements.

The carapace is flat and completely ossified. The nuchal plate is always conspicuous, much larger than the neurals, and these are often reduced by being encroached upon by the eight pairs of costal plates, which then meet in the dorsal line. In _Sternothaerus_ all the eight neurals are present and form a continuous row. In most of the other genera they are reduced to seven, the last being squeezed out. In _Rhinemys_ they are reduced to the second, third and fourth and an isolated fifth, and in _Hydraspis_ they are all gone. The pygal plate is always, even in _Sternothaerus_, separated from the last neural by the eighth pair of costals. The marginals number 23, but in _Carettochelys_ only 21.

The carapace is covered with horny shields, except in _Carettochelys_. The nuchal is absent in the Pelomedusidae and in a few Chelydidae (_Elseya_ and a few species of _Emydura_). In _Hydromedusa_ the nuchal is shut in by the anterior marginals, simulating a sixth neural. The plastron is composed of the usual nine elements, but the Pelomedusidae possess an additional pair, the meso-plastra, inserted between the hyo- and hypo-plastra. The bridge is strong, connected with the carapace by suture. In _Sternothaerus_ the front lobe of the plastron is movable. The intergular shield is always present; it is terminal, forming part of the front margin, except in _Chelodina_, where this shield, although large, is shut in behind the gulars (cf. Fig. 61, 4 and 5, p. 315).

Although the Pleurodira are a peculiarly specialised group, one of the oldest Chelonian fossils known seems to belong to them. _Proganochelys_, represented by a complete shell, nearly 2 feet long, has been found in the Upper Keuper Sandstone of Würtemberg. _Plesiochelys_, of the Upper Jurassic of Switzerland, has eight neural and three supracaudal plates, but is without the {390}ischiadic plastral ankylosis. _Pleurosternum_, of the English and Continental Purbeck beds, has meso-plastral plates like the recent Pelomedusidae. _Rhinochelys_, of the Cambridge Greensand, has a broad parieto-postfrontal roof, and large nasal bones. Forms like _Podocnemis_, now restricted to South America, occur in the Eocene of Europe. One of the most aberrant Chelonians is _Miolania_, from the Plistocene of Queensland and from Lord Howe's Island, remarkable for its huge size and the thick armour on the head and tail; the head especially carries large paired projections, one pair of which extends horizontally like powerful horns, recalling the queer Theromorphous _Elginia_.

We divide the recent Pleurodira into three families, of which that of _Carettochelys_ stands apart by its paddle-shaped limbs and the absence of horny shields. The Pelomedusidae and Chelydidae are closely allied. The former are not Australian, and are externally distinguished by the absence of a nuchal shield.

FAM. 1. PELOMEDUSIDAE.–Neck completely retractile within the shell. Carapace without a nuchal shield. The plastron is composed of eleven plates, there being besides the unpaired endo-plastron a pair of meso-plastra, situated between the hyo- and hypo-plastra; but these meso-plastra meet in the middle line in _Sternothaerus_ only, while in _Podocnemis_ and _Pelomedusa_ they are restricted to small pieces on the bridge, widely separated from each other by the usual hyo- and hypo-plastral suture. A nuchal shield is absent; there are twenty-four marginal and thirteen plastral shields, inclusive of the conspicuous intergular. The temporal fossa is widely open, except in _Podocnemis_, where it is partly roofed in by the meeting of the much-expanded quadrato-jugal with the parietal. The palatine bones are in median contact, not separated by the vomer. Nasal bones being absent, the large prefrontals meet in the middle line. The second cervical vertebra is biconvex.

This family is now represented by only three genera, with about fifteen species in Africa, Madagascar, and South America.

_Sternothaerus._–Skull without a bony supratemporal roof. Meso-plastra large, extending right across the plastron. Anterior lobe of the plastron movable, the hinge passing between the hyo- and meso-plastral plates, and between the pectoral and abdominal shields. Fore- and hind-limbs with five short digits and claws. Several species in tropical and southern Africa, and {391}in Madagascar. _S. derbianus_ in West Africa, from the Gambia to Angola, is the largest species, with a shell nearly one foot in length.

_Pelomedusa._–Skull with a slender parieto-squamosal arch. Meso-plastra small and lateral. Plastron without a hinge. Fore- and hind-limbs with five very short digits and five claws. Top of the head with one pair of shields between the eyes, and with a large interparietal and a pair of parietals behind.

_P. galeata_, the only species, occurs in Madagascar and nearly the whole of Africa south of the Sahara, from the Cape to Abyssinia, and in the Sinaitic peninsula. The shell, less than one foot in length, is much depressed and is obtusely keeled; brown above with black spots; brownish-yellow below. The short and broad head is coloured like the rest, without ornamentation. In Somaliland this species sleeps hidden on land during the dry seasons, from July to the end of September, and from January to March, and appears at once after the rains have set in.

_Podocnemis._–With a supratemporal roof formed by the junction of the parietal with the quadrato-jugal. Meso-plastra small and lateral. Fore- and hind-limbs broadly webbed, with five and four claws respectively. The fore-arms and the outer edges of the hind-feet with several conspicuous shields, hence the generic name. Head with an interparietal, two parietals, and a narrow unpaired shield between the eyes. The tail is very short. The carapace is flat and broad, strongly serrated on the posterior margin. Chin with one or two short barbels. Several species in South America, chiefly in the basin of the Amazon, and one in Madagascar.

_P. expansa._–Very common in Tropical South America, east of the Andes. The female, which is much larger than the male, has a shell nearly three feet in length. Olive-brown above with darker patches; yellowish below. With a few yellow spots above and behind the eyes, and on the parietal region. The "Arrau" turtle is of great commercial importance on account of the eggs, which are periodically collected in enormous quantities, chiefly for the oil. This is either eaten, like the eggs themselves, or used for burning in lamps, or as an addition to tar. The turtles are likewise eaten by man and beast. Thousands of the little creatures are snapped up by Jabiru storks, alligators, and fishes; the adults fall an easy prey {392}to the prowling jaguar, which turns them over on to their backs and neatly cleans out the flesh with its sharp and powerful claws.

Fertilisation takes place in the water, the eggs are deposited on land, in sand-banks, the female digging a hole about two feet deep and covering up the numerous soft-shelled eggs with sand. The time of deposition is the early hours of the morning, but the season depends upon the beginning of the principal rains, since the young are hatched shortly before the torrential rains. This season differs considerably in the various countries. The hatching takes about forty days; the eggs are consequently laid in the Amazon countries during the months of September to November, in the Orinoco district in March. This species lives in the pools of the inundated forests, and when these are dried up, the animals retire into the rivers themselves. Their food consists mainly of the fruit dropping down from the trees.

Bates, in his delightful book, _The Naturalist on the River Amazon_, gives the following lively and exhaustive account of his experience with these turtles:–

"I accompanied Cardozo in many wanderings on the Solimoes, during which we visited the 'praias' (sand islands), the turtle pools in the forests, and the by-streams and lakes of the great desert river. His object was mainly to superintend the business of digging up turtle eggs on the sandbanks, having been elected commandant for the year by the municipal council of Ega, of the 'praia real' of Shimuni, the one lying nearest to Ega. There are four of these royal praias within the Ega district, a distance of 150 miles from the town, all of which are visited annually by the Ega people for the purpose of collecting eggs and extracting oil from their yolks. Each has its commander, whose business is to make arrangements for securing to every inhabitant an equal chance in the egg harvest, by placing sentinels to protect the turtles whilst laying, and so forth. The pregnant turtles descend from the interior pools to the main river in July and August, before the outlets dry up, and there seek in countless swarms their favourite sand-islands; for it is only a few praias that are selected by them out of the great number existing. The young animals remain in the pools throughout the dry season. These breeding places of turtles then lie 20 to 30 or more feet above the level of the river, {393}and are accessible only by cutting roads through the dense forest....

"We found the two sentinels lodged in a corner of the praia, where it commences at the foot of the towering forest-wall of the island, having built for themselves a little rancho with poles and palm-leaves. Great precautions are obliged to be taken to avoid disturbing the sensitive turtles, who, previous to crawling ashore to lay, assemble in great shoals off the sand-bank. The men, during this time, take care not to show themselves, and warn off any fisherman who wishes to pass near the place....

"I rose from my hammock by daylight, shivering with cold; a praia, on account of the great radiation of heat in the night from the sand, being towards the dawn the coldest place that can be found in this climate. Cardozo and the men were already up watching the turtles. The sentinels had erected for this purpose a stage about fifty feet high, on a tall tree near their station, the ascent to which was by a roughly made ladder of woody lianas. They are enabled, by observing the turtles from their watch-tower, to ascertain the date of successive deposits of eggs, and thus guide the commandant in fixing the time for the general invitation to the Ega people.

"The turtles lay their eggs by night, leaving the water, when nothing disturbs them, in vast crowds, and crawling to the central and highest part of the praia. These places are, of course, the last to go under water when, in unusually wet seasons, the river rises before the eggs are hatched by the heat of the sand.... The hours between midnight and dawn are the busiest. The turtles excavate with their broad webbed paws deep holes in the fine sand; the first-comer, in each case, making a pit about three feet deep, laying its eggs (about 120 in number), and covering them with sand; the next making its deposit at the top of that of its predecessor, and so on until every pit is full. The whole body of turtles frequenting a praia does not finish laying in less than fourteen or fifteen days, even when there is no interruption. When all have done, the area (called by the Brazilians 'taboleiro') over which they have excavated is distinguishable from the rest of the praia only by signs of the sand having been a little disturbed.

"I mounted the sentinel's stage just in time to see the turtles retreating to the water on the opposite side of the sand-bank, {394}after having laid their eggs. The sight was well worth the trouble of ascending the shaky ladder. They were about a mile off, but the surface of the sands was blackened with the multitudes which were waddling towards the river; the margin of the praia was rather steep, and they all seemed to tumble head first down the declivity into the water.... Placards were posted up on the church doors at Ega, announcing that the excavation on Shimuni would commence on the 17th of October, and on Catuá, sixty miles below Shimuni, on the 25th. By the morning of the 17th some 400 persons were assembled on the borders of the sand-bank, each family having erected a rude temporary shed of poles and palm-leaves to protect themselves from the sun and rain. Large copper kettles to prepare the oil, and hundreds of red earthenware jars, were scattered about on the sand.

"The excavation of the taboleiro, collecting the eggs, and purifying the oil, occupied four days. All was done on a system established by the old Portuguese governors, probably more than a century ago. The commandant first took down the names of all the masters of households, with the number of persons each intended to employ in digging; he then exacted a payment of 140 reis (about 4d.) a head towards defraying the expense of sentinels. The whole were then allowed to go to the taboleiro. They ranged themselves round the circle, each person armed with a paddle, to be used as a spade, and then all began simultaneously to dig on a signal being given–the roll of drums–by order of the commandant. It was an animating sight to behold the wide circle of rival diggers throwing up clouds of sand in their energetic labours, and working gradually towards the centre of the ring. A little rest was taken during the great heat of mid-day, and in the evening the eggs were carried to the huts in baskets. By the end of the second day the taboleiro was exhausted; large mounds of eggs, some of them four to five feet in height, were then seen by the side of each hut, the produce of the labour of the family.

"In the hurry of digging, some of the deeper nests are passed over; to find these out, the people go about provided with a long steel or wooden probe, the presence of the eggs being discoverable by the ease with which the spit enters the sand. When no more eggs are to be found, the mashing process begins. {395}The egg, it may be here mentioned, has a flexible or leathery shell; it is quite round, and somewhat larger than a hen's egg. The whole heap is thrown into an empty canoe and mashed with wooden prongs; but sometimes naked Indians and children jump into the mass and tread it down, besmearing themselves with yolk, and making about as filthy a scene as can well be imagined. This being finished, water is poured into the canoe, and the fatty mass is then left for a few hours to be heated by the sun, on which the oil separates and rises to the surface. The floating oil is afterwards skimmed off with long spoons, made by tying large mussel-shells to the end of rods, and purified over the fire in copper kettles.

"The destruction of turtle eggs every year by these proceedings is enormous. At least 6000 jars, holding each three gallons of the oil, are exported annually from the Upper Amazons and the Madeira to Para, where it is used for lighting, frying fish, and other purposes. It may be fairly estimated that 2000 more jarfuls are consumed by the inhabitants of the villages on the river. Now, it takes twelve basketfuls of eggs, or about 6000, by the wasteful process followed, to make one jar of oil. The total number of eggs annually destroyed amounts, therefore, to 48 millions. As each turtle lays about 120, it follows that the yearly offspring of 400,000 turtles is thus annihilated. A vast number, nevertheless, remain undetected; and these would probably be sufficient to keep the turtle population of these rivers up to the mark, if the people did not follow the wasteful practice of lying in wait for the newly-hatched young, and collecting them by thousands for eating; their tender flesh, and the remains of yolk in their entrails, being considered a great delicacy. The chief natural enemies of the turtle are vultures and alligators, which devour the newly-hatched young as they descend in shoals to the water. These must have destroyed an immensely greater number before the European settlers began to appropriate the eggs than they do now. It is almost doubtful if this natural persecution did not act as effectively in checking the increase of the turtle as the artificial destruction now does. If we are to believe the tradition of the Indians, however, it had not this result; for they say that formerly the waters teemed as thickly with turtles as the air does now with mosquitoes. The universal {396}opinion of the settlers on the Upper Amazon is, that the turtle has very greatly decreased in numbers, and is still annually decreasing.

"The principal object of another expedition was to search certain pools in the forest for young turtle. We started from the praia at sunrise on the 7th of October in two canoes, containing twenty-three persons, nineteen of whom were Indians. The pool covered an area of about four or five acres, and was closely hemmed in by the forest, which, in picturesque variety and grouping of trees and foliage, exceeded almost everything I had yet witnessed. The margins for some distance were swampy, and covered with large tufts of fine grass. The pool was nowhere more than five feet deep, one foot of which was not water, but extremely fine and soft mud.

"Cardozo and I spent an hour paddling about. The Indians seemed to think that netting the animals, as Cardozo proposed doing, was not lawful sport, and wished first to have an hour or two's old-fashioned practice with their weapons. I was astonished at the skill which they displayed in shooting turtles from little stages made of poles and cross pieces of wood. They did not wait for their coming to the surface to breathe, but watched for the slight movements in the water which revealed their presence underneath. These little tracts on the water are called the siriré; the instant one was perceived an arrow flew from the bow of the nearest man, and never failed to pierce the shell of the submerged animal. When the turtle was very distant, of course the aim had to be taken at a considerable elevation, but the marksmen preferred a longish range, because the arrow then fell more perpendicularly on the shell, and entered it more deeply.

"The arrow used in turtle-shooting has a strong lancet-shaped steel point fitted into a peg, which enters the tip of the shaft. The peg is secured to the shaft by twine, being some thirty or forty yards in length, and neatly wound round the body of the arrow. When the missile enters the shell the peg drops out, and the pierced animal descends with it towards the bottom, leaving the shaft floating on the surface. This being done the sportsman paddles in his canoe to the place, and gently draws the animal by the twine, humouring it by giving it the rein when it plunges, until it is brought again near the surface, when {397}he strikes it with a second arrow. With the increased hold given by the two cords he has then no difficulty in landing his game.

"By mid-day the men had shot about a score of nearly full-grown turtles. Cardozo then gave orders to spread the net.... Three boat loads, or about eighty, were secured in about twenty minutes. They were then taken ashore and each one secured by the men tying the legs with thongs of bast.

"When the canoes had been twice filled we desisted after a very hard day's work. Nearly all the animals were young ones, chiefly, according to the statement of Pedro, from three to ten years of age; they varied from 6 to 18 inches in length, and were very fat. Cardozo and I lived almost exclusively on them for several months afterwards. Roasted in the shell they form a most appetising dish. These younger turtles never migrate with their elders on the sinking of the waters, but remain in the tepid pools, fattening on fallen fruits, and, according to the natives, on the fine nutritious mud. We captured a few full-grown mother turtles, which were known at once by the horny skin of their breast plates being worn, telling of their having crawled on the sand to lay eggs the previous year. They had evidently made a mistake in not leaving the pool at the proper time, for they were full of eggs, which, we were told, they would, before the season was over, scatter in despair over the swamp. We also found several male turtles, or capitaris, as they are called by the natives. These are immensely less numerous than the females, and are distinguishable by their much smaller size, more circular shape, and the greater length and thickness of their tails. Their flesh is considered unwholesome, especially to sick people having external signs of inflammation."

The most recent account of these water tortoises is that published by Dr. Goeldi from the MS. of João Martins da Silva Continho, a former resident at Manáos on the Middle Amazon. The "Tartaruga" (the Portuguese name for turtles) live from January to July in the inundated, quiet backwaters of the forest-region, feeding upon the various seeds of palms as these ripen and drop successively; rarely, and only when hard up, they are carnivorous. The creatures hide under water below the trees, when they are espied by the Indians, who dive down to a depth of twenty and more feet to catch them in their arms. The {398}civilised Indians use a steel-pointed lance of hard wood, about 10 feet in length. A string connects the point with the shaft around which it is wound. When stuck into the tortoise the shaft and point part; the string is either tied to the boat or to a little float of light wood. In other districts an arrow with a string is employed.

In August, when the water subsides, the tortoises return to the rivers, and the entrance of the lagoon is closed with nets. A number of boats with long poles drive them with much noise towards the entrance. On their way to the rivers the tortoises always go up-stream, and this is called the "arribaçaõ das tartarugas," the ascent of the turtles. The fishermen post themselves at shallow spots or on sand-banks, and wait for the creatures which come up to find a place for landing and laying. The arrows employed are called _sararaca_, _i.e._ a thing which can be disjointed; they are about 4 feet long, and consist of a _gomo_ or internodium of wood 9 inches long with a one- or two-barbed steel point, and the shaft into which the _gomo_ fits loosely. The _gomo_ is, moreover, connected with the shaft by a string made of palm-fibres about 30 feet in length, partly wound round the shaft, which ultimately acts as a float.

The laying takes place from the end of September into October. Some of the parents seem to reconnoitre on land for a few days. As a rule only females do this, and the natives say that they are led by a "_mestra_." The laying takes place early in the morning. The number of females is so great that they often block the way of the boats, and make a great noise by knocking against their neighbours' shells. Each digs a hole about 18 inches or 2 feet deep, and lays from 80 to 200 eggs. Sometimes the laying individual is entirely buried by its neighbours which are scraping their own holes.

In some districts the eggs are wanted for "manteiga" (Portuguese for butter); and the turning over, or _viraçaõ_ of the tortoises takes place later. In other districts they are caught before the eggs are laid, and this barbaric and destructive custom was formerly forbidden by the people themselves. Although the provincial assembly tried to reinstitute the old reasonable customs, the inspectors are often got over by bribery.

There are two ways of extracting the oil from the eggs. To get the thick oil used, mixed with tar, for shipbuilding, caulking, {399}etc., the eggs are heaped up for five days and then worked. The fluid oil for lighting is made from fresh eggs, which are put into a boat and then trampled out with the feet. The oil is drawn off into large earthen jars and put on the fire. Then it is rapidly cooled. The best oil, used for frying fish, is that which is gained from the roasted tortoises themselves. Fresh eggs are either fried or taken with sugar, or mixed with manioca-flour and water. The young, which are hatched in January, are likewise eaten fried, or they are preserved in the fat of the parents.

An average tortoise yields 5 lbs. of fat, costing on the spot two milreis. The whole full-grown animal, of one yard in length, costs the same, and its meat is sufficient to sustain a family of six people for three days. To make 24 lbs. of oil requires 3000 eggs. Two or three tortoises would yield the same amount from their fat. Consequently the destruction of the eggs causes an enormous waste, and is after all the least economical procedure. In the year 1719, 192,000 lbs. were exported from the Alto Amazonas, representing 24,000,000 eggs. In 1700 there were still plenty of tortoises 50 leagues above the mouth of the Para river. Now there is no assembly of more than fifteen tortoises to be found anywhere within 300 leagues from Para to the mouth of the Rio Negro. On the Rio Madeira, from the mouth to the first cataract, 186 leagues distance, there are now only two regular nesting localities. The upper Solimoes and the Rio Yapura are still rich. Near Ega are regular tortoise-ponds, called "curral," which yield sufficient support to their owners; the animals are fed with manioca-flour and leguminous plants.

FAM. 2. CHELYDIDAE.–The neck bends under the margin of the carapace, but remains partly exposed. The nuchal shield is absent except in two Northern Australian species. There are twelve pairs of marginal shields. The plastron is composed of nine plates, and is covered with thirteen shields, one of which is the conspicuous intergular. The temporal region of the skull shows great diversity. It is quite open in _Chelodina_, covered in by broad expansions of the parietal bones in _Platemys_, _Emydura_, and _Elseya_, or bridged over by a parieto-squamosal arch, which is very slender in _Rhinemys_, strong in _Chelys_ and _Hydraspis_. The palatine bones are separated by the vomer; the nasals are variable, mostly present, but the prefrontals are always small, and separated {400}by the frontals. The fifth and eighth cervical vertebrae are biconvex.

This family, still represented by nearly thirty species, which are divided into eight genera, is restricted to Notogaea, namely, South America and Australia.

[Illustration: FIG. 87.–Skull of _Chelys fimbriata_. × 1. A, Dorsal view of skull; B, side view of skull and hyoid apparatus. _Cop_, copular piece; _F_, frontal; _J_, jugal; _L.o_, lateral occipital; _Mand_, mandible; _Op_, opisthotic; _Orb_, orbit; _Par_, parietal; _Pt.f_, postfrontal; _Ptg_, pterygoid; _Q_, quadrate; _Qj_, Quadrato-jugal; _Sq_, squamosal; I, II, First and second branchial arch.]

_Chelys fimbriata_, the "Matamata," the only species of this genus, inhabits the rivers of Guiana and Northern Brazil. Besides the nuchal, there are seven neural plates; the last pair of costals form a median suture. Nasal bones are absent. The jaws are very weak. The Matamata has a very peculiar appearance. The nose is produced into a long, soft tube, at the end of which open the tiny nostrils. The eyes are very small, and the orbits are placed very near the anterior end of the skull, while the parietal {401}region is broad and much elongated (Fig. 87, p. 400). The quadrates are drawn out into trumpet-shaped tubes. The hyoid apparatus is very large, with enormous anterior and posterior horns. The head and neck are as long as or even longer than the carapace, which is covered with thick, lumpy shields. The skin of the thick neck, of the sides and under parts of the head, is produced into many soft arborescent excrescences or fimbriae, those of the chin and throat and the large ear-flaps being movable at will, and probably used to attract fishes and other prey. The tail is very short. The fore- and hind-limbs are webbed, the former with five, the latter with four claws. Old specimens, which reach a total length of three feet, are uniformly dark brown, and look like a log covered with rough bark. The young are far less ugly, with black and yellow spots on the shell, and with dark stripes along the neck.

[Illustration: FIG. 88.–_Chelys fimbriata_ ("Matamata"). × ⅒.]

Very little is known about the habits of this peculiar creature. It is said to lie submerged in the water, waiting for fishes, frogs, or tadpoles, which are attracted by the playing motions of its cutaneous excrescences. The jaws being so weak, and being covered with a partly soft lip-like skin, it is probable that they are not used for seizing the prey, but that the latter is engulfed into the mouth with the inrush of water into the throat. {402}That this can be widened enormously is indicated by the greatly developed hyoid apparatus.

_Chelodina._–The neck is long and slender, the head small and smooth. The nuchal is terminal; the intergular is large. The neural plates are completely suppressed, all the eight pairs of costal plates meeting in the middle line. The shell is very flat. Anterior and posterior limbs entirely webbed, and with only four claws. The tail is very short. Three species in Australia, one in New Guinea.

[Illustration: FIG. 89.–_Chelodina longicollis._ × ⅓.]

_Ch. longicollis_ reaches a shell-length of ten inches. It inhabits Southern Australia. The illustrations make a detailed description unnecessary. The colour of the dorsal shield is uniformly dark rich brown, while the shields of the under surface are yellow, with broad dark brown lines along the sutures. These "long-necked Chelodines" have a striking appearance, when they swim or creep about, with the neck either stretched out straight or bent horizontally in an S-shape. The whole creature looks neat and elegant; the iris is pale yellow, and gives the eye a very intelligent expression. They keep well in captivity, provided they are given the choice of land and water. My own prefer to spend most of the day on land, preferably under the ledge of a stone, or perched upon the stone itself if the latter is in the shade, and not too much exposed to view. There they lie motionless, with the neck neatly tucked under the shell, either to the right or to the left. Although the eyelids may be closed, they can see well enough, owing to the transparent condition of the lower lid. They feed in the water upon soft animals, as for instance worms, smooth caterpillars, cockroaches or little frogs; and they also take meat readily, provided this is moved about. The food is invariably taken with a quick sideward jerk of the neck and head.

{403}[Illustration: FIG. 90.–_Chelodina longicollis_ (Australian long-necked Chelodines). × ¼.]

My specimens soon became so tame that they left the water, and ran up to me with the necks stretched to their full length, then snatching the bit of food, and retiring into the pond to swallow it. When left to themselves they are rather nocturnal in their feeding habits. Now and then they tuck themselves away for weeks without feeding, for instance when they go through a regular term of {404}aestivation in the summer. The last winter they spent buried in the moss, but occasionally, especially on bright and sunny days, they went into the water for a few hours, chiefly to drink, but sometimes also to take a little food.

_Hydromedusa_, a South American genus, has a neck even longer than that of _Chelodina_, which it much resembles externally. But the nuchal shield, large and broad transversely, is situated behind the anterior marginals, looking therefore like a sixth neural shield. The neural plates form a continuous row, only the last pair of costal plates meeting in the middle line. _H. tectifera_ occurs in Southern Brazil, and in the La Plata. The shell is dark brown above; yellowish, with dark spots, below; the head and neck are olive-coloured, adorned with a broad white, black-edged band on either side. Fore- and hind-limbs broadly webbed, and with four claws. Total length of the shell about eight inches.

FAM. 3. CARETTOCHELYDIDAE.–The shell is covered with soft skin instead of horny shields. The limbs are transformed into paddles, with elongated digits, and have only two claws. The neck is short, and not retractile. In other respects the skeleton, notably the plastron, pelvis, and skull, conform with the Pleurodirous type. Only one species, _Carettochelys insculpta_, still imperfectly known, from the Fly River, New Guinea. Length of the shell of the only complete specimen about 18 inches. This peculiar creature seems to stand in the same relation to the typical Pleurodira, as do the Chelonidae to the Testudinidae, except for the complete reduction of the horny shields upon the shell, recalling in this respect _Sphargis_ and _Trionyx_.

SUB-ORDER 3. TRIONYCHOIDEA.–The shell is very flat, oval, or almost round, and is covered with soft, leathery skin instead of with horny shields. The limbs are broadly webbed, and only the three inner digits are provided with claws. Carnivorous, found in the rivers of Asia, Africa, and North America.

The head and neck are completely retractile, bending by a sigmoid curve in a vertical plane like that of the Cryptodira. The jaws are concealed by soft, lip-like flaps, and the nose forms a soft short proboscis. The ear is hidden. The skull, Fig. 91, is flat, with three long posterior processes, formed by the supra-occipital above, and the squamosals on either side. The whole temporal region forms a wide, shallow fossa, without any {405}indication of being arched or bridged over. The premaxilla is extremely small, unpaired, not even reaching the nasal cavity or the vomer. The maxillaries are correspondingly enlarged, surrounding the choanae, which are separated by the narrow vomer. The palatines form a median suture, and are joined behind by the long basisphenoid, which separates the long pterygoids from each other. The quadrate is trumpet-shaped, with a posterior notch for the stapes. The zygomatic arch is complete, and is formed by the quadrato-jugal and the jugal; the latter joins the maxillary and postfrontal, mostly reaching the orbit; in some cases it also just meets the parietal, thereby adding to the strength of the postorbital arch. The prefrontals are large; nasals are absent. The mandible is remarkable for the great development of the coronoid process.

[Illustration: FIG. 91.–Skull of _Trionyx hurum_. _A_, From above; _B_, from the left side; _Cond_, occipital condyle; _Fr_, frontal; _J_, _Jug_, jugal; _L.o_, lateral occipital; _Max_, maxillary; _Op.o_, opisthotic; _Par_, parietal; _Pr.f_, prefrontal; _Pro_, prootic; _Pt.f_, postfrontal; _Q_, quadrate; _Qj_, quadrato-jugal; _S.o_, supra-occipital; _Sq_, squamosal.]

The pubic and ischiadic bones enclose a large heart-shaped foramen, and are free from the plastron; the ilia are attached only to the sacral ribs. The carapace is peculiar in so far as it is very incomplete peripherally, the ribs extending considerably beyond the costal plates, nor are they joined by marginal plates, which are absent, unless they are represented by a few small ossifications imbedded in the posterior marginal flap of the disc (_Emyda_ of India). The rim of the disc is always formed by a horizontal, cutaneous, very flexible flap. All the dorsal plates have a rough upper surface, vermiculated or rugose, as usual with such dermal bones, which have lost most of or all their horny covering, and have sunk more deeply into the skin. The {406}nuchal plate has usually a pair of rib-like processes. The neurals form a continuous series, except in the African _Cyclanorbis_, in which they are much reduced in size, and separated by the costal plates.

The plastron is imperfect, all its constituent nine elements being only loosely connected with each other, and there remains a wide median vacuity between the lateral elements. Most of these plastral bones are reduced to splints, which, instead of meeting by regular sutures, loosely interdigitate with their jagged edges. In the young all these ventral elements are deeply imbedded in the soft, leathery skin, and they do not at all resemble in appearance those of the dorsal side. With age they develop upon their ventral surface stronger and denser ossifications, which ultimately broaden out, sometimes beyond the original underlying bone, and assume the characteristic vermiculated surface-appearance. This is undoubtedly a process of exostosis, a step towards revival of that armour which had been much reduced ancestrally. To appreciate this condition, it is at least suggestive that these mud-tortoises, when kept in the usual hard-bottomed tanks, invariably become sore, the skin wearing through where the imbedded plastral bones touch the ground. Thus what is crammed into the short life of a captive individual, is in the natural course of events spread over many generations, whereby it has ceased to be pathological, and has become a comparatively new, tertiary, but regular feature.

It is not open to much doubt that the characteristic features of the Trionychoidea are not primitive but secondary. This is indicated by the whole structure and behaviour of the carapace and plastron. The softening of the whole shell, the loss of the horny shields, the reduction of the claws, are the direct and almost unavoidable results of life in muddy waters.

Geologically they do not seem to be very old. They appear, already referable to the genus _Trionyx_, in the Upper Cretaceous strata of North America. In the Lower and Middle Tertiary strata many species existed in North America and in Europe, and it is of great importance that in these species the costal plates were much broader, and the marginal plates better developed, than in the recent forms. Now their half-dozen genera, with about twenty-four species, are confined to North America, the tropical and warmer parts of Asia, and the Malay {407}Islands, and to Africa from the Nile to the Senegal and to the Congo.

The habits of Trionychoidea have found few observers. According to L. Agassiz,[138] they live in the muddy bottom of shallow waters, burying themselves in the soft mud, with only the head, or a small part of it, exposed. They breathe without moving the body, by raising up the long neck and carrying the leathery snout above water. When moving through the water they strike horizontally with both pairs of limbs, alternating, however, the right and left; but when they start suddenly, the front limbs are seen moving together towards the tip of the snout, and then striking simultaneously backward with great power. As the shield does not project forward, the fore-limbs usually move beyond the shield, and as its outer edge is sharp, and the feet are broad, their webs reach above as well as below the plane of that edge, so that the water is driven partly over and

## partly under it. When they move along the bottom, the limbs still move

horizontally, the webs striking against the water, and the inner toes, those with the claws, against the bottom. They also bury themselves horizontally, becoming covered by only a thin layer of mud. They readily resort to the shell for protection. The neck and head are withdrawn entirely, the loose skin rolling off from the greater part of the neck; and the skin of the legs also slips off, as far as the elbows and knees. In confinement they exhibit great quickness; their movements are abrupt and unsteady, except when they swim rapidly in one direction. They then dart their long and slender neck quickly forwards or sideways and upwards, as snakes do, and bite in the same way, striking suddenly. Their temper is bad or even ferocious, and large specimens are quite dangerous.

Their food consists of all sorts of aquatic animals, fish, frogs, and molluscs, for instance _Anodonta_ and _Paludina_. According to the different diet, many species develop a peculiar kind of dimorphism, a reasonable explanation of which has been given by Boulenger. In the young the horny coverings of the jaws are sharp, with cutting edges, and in those specimens which keep to a diet of fish and other soft creatures, the jaws remain in the same condition. But in those which take to living upon molluscs, the hard shells of which they have to crush, the horny edges are {408}worn down; and broad, thick, horny, crushing pads are developed in their stead, the supporting parts of the jaws becoming more massive. The masticatory muscles are likewise enlarged, and a tubercle grows upon the lower border of the jugal bone, whence arises part of the masseter muscle.

The eggs are round, thick-shelled, but very brittle; they are laid in the sand above the level of the water, and this is the chief occasion on which these tortoises creep on land.

_Trionyx._–The plastron has no special cutaneous valves for the concealment of the hind-limbs. This is the principal genus, with the greatest number of species and the widest distribution, the latter coinciding with that of the whole family. The upper surface of the shell of young specimens frequently forms numerous longitudinal ridges or series of little horny tubercles which disappear with age.

_T. ferox_, the commonest "Soft-shelled Turtle" of the United States. Olive above with scattered, small, round, black spots; young with conical, spine-like tubercles, especially on the nuchal border and on the posterior portion of the shell, which has a pale, black-edged border. A light, black-edged streak passes through the eye and joins its fellow on the snout. The limbs are olive brown, spotted and marbled with black. The under parts of the shell are white. Very large specimens have a shell 18 inches in length and 16 inches wide. Holbrook gives the following account of its habits:–

"A voracious, carnivorous creature. They reside most constantly in the water, swim with rapidity, and choose for their retreat holes under the banks of rivers, or under rocks; and not unfrequently the trunk of some huge forest tree, fallen into the stream, affords them shelter. Sometimes they leave the water and conceal themselves in the mud: I have frequently seen them thus buried to the depth of 2 or 3 inches, leaving only a small breathing hole for the long neck and narrow head, which is occasionally thrust out, but most commonly it is retracted so that one would pass near without observing their habitation; and if seen, it might easily be mistaken for the residence of some large insect. At other times they may be seen in numbers on rocks in shallow water, basking in the sun, apparently asleep. They bite severely when provoked, darting forward with great velocity the long neck and head, and not unfrequently spring upward at the same time and make a loud hiss.

{409}[Illustration: FIG. 92.–_Trionyx ferox_ (American Soft-shelled Turtle). × ⅒.]

In the month of May the females seek sandy places along the banks of the waters they inhabit to lay their eggs, generally about sixty in number; and it is remarkable that, though their motions are slow and difficult on dry land, yet at this season they sometimes mount hillocks several feet high. The flesh affords the most delicate food, surpassing that even of the Green Turtle. The geographical distribution is interesting. It inhabits the Savannah as well as all those rivers that empty into the northern borders of the Gulf of Mexico; it ascends up the broad Mississippi, and is found in all its tributaries, even to the very foot of the Rocky Mountains; it abounds in the chain of great northern lakes both above and below the Falls of Niagara, and is common in the Mohawk, a tributary of the {410}Hudson river; but it is not found in any other Atlantic stream between that and the Savannah river, a distance of nearly 800 miles."

_T. triunguis_, the only African species, ranging from the Senegal and Congo into the Nile-system, but occurring also in Syria, is perhaps the largest of all Trionychidae, reaching a shell-length of almost 3 feet. The adults are olive-brownish above, the throat and under parts of the shell with round, white spots separated by a dark network. The young have whitish specks and spots.

[Illustration: FIG. 93.–_Trionyx gangeticus_ (young). × ⅓.]

_T. gangeticus_ and _T. hurum_ are the principal Indian species. The former is the larger of the two, with a shell of more than 2 feet in length; olive above, the young with fine black vermiculations; head with a black longitudinal streak from between the eyes to the nape, intersected by two or three chevron-shaped black streaks; under parts yellowish. _T. hurum_ is olive brown above {411}and below, in younger specimens with conspicuous, large, yellow spots on the sides of the head. The young are ornamented with two or three pairs of large round spots on the back, and the same applies to the beautiful young of the Burmese, _T. formosa_.

[Illustration: FIG. 94.–_Trionyx formosa_ (young). × 1.]

The three genera, _Cycloderma_ and _Cyclanorbis_ of Tropical Africa, and _Emyda_ of India, have a pair of cutaneous femoral valves or flaps on the plastron, beneath which the hind-limbs are withdrawn.

{412}