74 



MUSEUM OF ANIMATED NATURE. 



[Tortoises. 



CLASS REPTILIA (REPTILES). 



We now advance to another department of our 

 Pictorial Museum, and enter upon our collection of 

 Reptiles— a sincular class of beines, ])resenting the 

 most wonderful variety of form and structure, and 

 consequently adapted for different habits of life, 

 different localities, and ditferent modes of loco- 

 motion. We may take by way of examples the 

 Tortoise, the Lizard, the Snake, and the Frog : the 

 contrast is startlini;, and we are ready to >ay— Can 

 these forms be comprehended together under one 

 natural (treat group or class, or are they not examples 

 of distinct classes? We may observe, that many 

 naturalists, and among them Mr. Bell, Mr. Gray, 

 and othere. regard the Frogs, Newts. Protei, &c., as 

 a distinct class, under the iitle Amphibia ; while, on 

 the other hand, Brongniart, Cuvier, Oppel, and 

 others, place the Amphibia as an order or section 

 (vithin the pale of the Reptilia. Moreover, between 

 the long, twining snakes, and the solid heavy, shiekl- 

 "Covered tortoises, the distance is very great ; much 

 greater than between any forms of the two previous 

 classes, viz., Mammalia and Birds; much greater 

 than between the elephant and mouse, the eagle 

 and humming-bird; almost, indeed, as much as 

 between the bird and quadruped, excepting that the 

 oviparous mode of reproduction obtains both in the 

 tortoise and snake, which, be it observed, is also 

 the case with birds — a pomt in which they exhibit 

 a certain degree of approximation to the Reptilia. 



Without entering into an analysis of the various 

 modes of arrangement which different naturalists 

 have instituted, all of which have their objections, 

 let us proceed to a general review of the common 

 characteristics of these animals, dividing them into 

 Tortoises (Chelonia), Lizards (Sauria), Serpents 

 (Ophidia), and Frogs (Amphibia). All are verte- 

 brate, with cold red blood, of a variable temperature ; 

 <)reathing by means of lungs, sometimes by bran- 

 chial tufts or gills : the skin is covered neither with 

 hair nor feathers, but with solid shields, horny 

 plates, scales, spines, or granules : otherwise, as in 

 the Amphibia, it is naked. The heart consists 

 essentially of two auricles and a ventricle. There 

 is either no external organ of hearing, or merely an 

 orifice, open in some, in othere covered with a 

 tympanic membrane, in a few protected by a move- 

 able valve. The limbs are variable ; four, two, or 

 none. The appetite is in general carnivorous ; some- 

 times, however, frugivorous. Of some the bite is 

 deadly. A high temperature is most congenial 1o 

 their nature, and it is in the hotter regions of the 

 globe that they abound in the greatest numbers, 

 both specifically and individually, and display the 

 most varied forms, the most gigantic bulk, and the 

 most dazzling colours. As our preliminary observ- 

 ations must be very brief, we shall at once pass to 

 our first order (perhaps subclass), hoping that as 

 we advance we shall gradually develop the cha- 

 racters of each in rotation. 



ORDER CHELONIA (TORTOISES) 



(xi'^'" 3. tortoise). These strange animals, as is 

 well known, are covered with natural armour, which 

 may be considered essentially a portion of the 

 osseous framework, thrown, as it were, outside of 

 the body, so as to constitute an external bony en- 

 velope or box, enclosing and protecting the internal 

 muscles and viscera, and covered on the outer surface 

 by plates of horny matter, scales, or a leathery ex- 

 pailsion. 



The box thus formed is composed of two portions : 

 an upper portion, called the buckler, back-plate, or 

 carapace (clypeus), composed of the vertebrae of 

 the back and loins, and also of the ribs, all ex- 

 panded and consolidated together ; a lower portion, 

 called the plastron, or breastplate (sternum), con- 

 sisting of nine osseous portions, eight in pairs, the 

 ninth single, and occupying the anterior part of the 

 plastron. The distinct bones forming the plastron 

 vary much, in different groups, in their consolida- 

 tion and degree of development ; it is in the land 

 tortoises that the solidity of this portion is at its 

 maximum. The same remark holds good with 

 respect to the carapace, which presents different 

 degrees of form, expansion, convexity, and of ex- 

 ternal covering in the several subordinate groups 

 and genera. 



The upper and under shields are in general 

 united at the sides, leaving before and behind a 

 space for the protrusion of the head, limbs, and tail ; 

 and these in general can be more or less completely 

 retracted under cover, and sometimes completely 

 shut up, either by the carapace or plastron being 

 transversely hinged. The union of the carapace 

 and plastron at the sides, is by means of what are 



termed costo-stemal bones, analogous perhaps to 

 the sternal ribs of the Sauria. 



Where the carapace is covered with plates or 

 scales, they are divided into vertebral, costal, and 

 marginal : the vertebral plates mnning longitudinally 

 down the centre, and five in number: the costal 

 plates are usually four, sometimes five, on each side ; 

 these are surrounded by the marginal plates con- 

 sisting of a nuchal plate, of a caudal plate, some- 

 times single, sometimes double, and of a variable 

 intermediate number. The plates of the plastron 

 and of the bones of union are variable. In the 

 marsh-tortoise those of the former are six on each 

 side, those of the latter two. In the loggerhead- 

 turtle they are more numerous and differently ar- 

 ranged. We shall give a better idea of the structure 

 of the carapace and plastron of these animals, and 

 of their connection with the skeleton, by referring to 

 our figures, than by any explanation. Fig. 2088 

 represents the Skeleton and Curapace of the Com- 

 mon Marsh Tortoise (Cistudo Europeea), seen from 

 below. 



Fig. 2089 represents the Skeleton and imperfect 

 Carapace of the Loggerhead Turtle (Chelone Caou- 

 ana), seen from below. 



Fig. 2090, the Carapace of the River Tortoise 

 (Trionyx, Geoffr. ; Gymnopus, Bibron), as seen from 

 below. In this group the osseous part of the cara- 

 pace is very much reduced, and flat, with an ex- 

 tensive cartilaginous circumference, the upper 

 surface being covered with a coriaceous membrane. 



Fig. 2091 is the Carapace of the common Bordered 

 Tortoise (Testudo marginaia), covered with its 

 horny shell. 



Fig. 2092 is the Carapace of the Loggerhead 

 Turtle (upper surface), covered with its horny plates 

 disposed in imbrications. 



Fig. 2093 represents the imperfectly developed 

 Sternum of the River Tortoise (Trionyx). 



Fig. 2094 is the still more imperfect Sternum of 

 the Loggerhead Turtle. 



Fig. 2095 is the complete Sternum of the Marsh 

 Tortoise (Cistudo Europasa). The contrast between 

 this and the two preceding is remaikable, yet in 

 each the essential components are the same. 



It may appear at first sight that there is a great 

 affinity between the armour, or rather box, in which 

 the tortoise is enclosed, and the coat of mail with 

 which many quadrupeds are covered, as for instance 

 the Armadilloes and the Chlarayphorus (See Chla- 

 myphorus, Fig. 2096). There is this important diffe- 

 rence ; — the coat of mail in these quadrupeds (Mam- 

 malia) is a simple horny addition to the skin itself, 

 resting upon and supported indeed by bold pro- 

 cesses of the skeleton ; whereas the osseous carapace 

 and plastron of the tortoise, however developed, are 

 part and parcel of the skeleton itself, which, as we 

 have said, is so modified as to protect the internal 

 organs, enclosing them as in a casket, which is itself 

 covered either with horny plates variously arranged, 

 or with a tough leathery skin, often thickened and 

 carried out beyond the circumference of the osseous 

 portions. Of the carapace of the tortoise Mercury 

 is fabled to have formed the ancient Grecian lyre, of 

 which one wilh only three strings, as given by 

 Mersenne, is represented at Fig. 2097. 



The lungs of the tortoise are very extensive, and 

 lie under the vaulted carapace, but it must be 

 evident that they cannot, from the immobility of the 

 carapace and sternum, be filled with air by any 

 action resembling that of quadrupeds or birds in 

 breathing, and in which the chest is alternately ex- 

 panded and contracted. The tortoise swallows or 

 gulps down air; the jaws being firmly closed, the 

 cavity of the mouth is enlarged by the drawing 

 down of the root of the tongue, and into the 

 vacuum thus formed the air rushes in through the 

 nostrils. The free part of the tongue is now applied 

 to the posterior orifices of the nostrils so as to stop 

 them, the gullet is also closed, the root of the 

 tongue is elevated, the broad muscles of the throat 

 contract, and the air is forced down the windpipe 

 into the lungs, which become filled by a repetition 

 of the process. The air is returned by the simple 

 pressure of muscles within the plastron and carapace. 

 It is in this manner that reptiles without ribs, as the 

 frog and toad, perform the act of breathing. 



The jaws of tortoises are not armed with teeth, 

 but cased in sharp-edged or serrated horny coverings, 

 enabling them to crop and mince the vegetable ali- 

 ment on which they feed. In some species of car- 

 nivorous appetite, as the Trionyx, there are thick 

 fleshy lips aiound this beak, and in one species, the 

 Matamata, the horny sheath is so rudimentary, that 

 many naturalists have overlooked it. 



The tongue of the tortoise is thick, fleshy, and 

 very movable, though not capable of protrusion ; it 



is abundantly supplied with nerves, and covered 

 with nervous papillee. It is provided with salivary 

 glands, and doubtless enjoys to a high degree the 

 sense of taste. 



With respect to smel), from the simplicity of the 

 olfactory organs, it appears to be but imperfect, 

 though sufficient for the necessities of the animal. 



Though the organs of hearing are not apparent 

 externally, they exist internally, and in a tolerably 

 perfect condition, yet tortoises appear by no means 

 to have the sense of hearing acute ; indeed the gi- 

 gantic tortoises on the Galapagos Islands are believed 

 by the inhabitants to be perfectly deaf, and Mr. 

 Darn in states that they certainly do not overhear a 

 person walking close behind them. 



Tortoises have the eye well developed and large ; 

 as in birds, it has an osseous ring, or circle of osseous 

 plates, around the ball, and is defended by a mem- 

 brana nictitans and two external eyelids; there are 

 also lachrymal glands. The pupil is circular. 



In the terrestrial tortoises the skull is broad across 

 the occiput, obtuse anteriorly, strong, and solid ; the 

 orbits are nearly circular, and the depression for the 

 reception of the vast temporal muscle is both deep 

 and extensive ; the occipital ridge is elevated ; the 

 cavity for the brain is contracted ; the articulating 

 condyle is a prominent tubercule ; the horny covering 

 of the upper jaw is strongly serrated, there being an 

 inner as well as an outer ridge, and the inner ridge 

 is received into a serrated channel of the horny 

 ridge of the lower jaw, the outer ridge, which is deep, 

 passing anteriorly, when the jaw is shut. This struc- 

 ture, reminding us of an array of real teeth, renders 

 the crushing and chopping up of vegetable aliment 

 easily effected. Figs. 2098, 2099, 2100, and 2101 

 represent the Skull of the Indian Tortoise, in pro- 

 file, as seen from above, as seen from below, and 

 as seen from behind. 



In the marine tortoises, or turtles, the cerebral 

 cavity may be said to have a double roof; for by a 

 production of the bones of the upper part of the « 

 head, a double vault is produced, within which, and 

 above the true surface of the cranium, are lodged the 

 temporal muscles of enormous volume, and to which 

 this vaulted roof forms an osseous envelope. This 

 structure gives to the skull an appearance of being 

 larger than it is in reality, for the cerebral cavity is 

 very small. In the Matamata (Chelys fimbriata) the 

 same peculiarity prevails ; the skull of this tortoise, 

 a fierce aquatic species, inhabiting the lakes, moras- 

 ses, and rivers of South America, is very remarkable. 

 It is extraordinarily large and flat, appearing as if it 

 had been crushed ; the small orbits are seated close 

 to the end of the muzzle ; the posterior region of the 

 cranium is elevated, in consequence of the vaulted 

 arrangement of the bones described. The cerebral 

 cavity is very trifling. Figs. 2102, 2103, 2104, and 

 2105, show the Skull of the Matamata in different 

 positions, viz. as seen from above, as seen from 

 below, in profile, and in a back view. In the back 

 view the vaulted structure is very distinguishable, 

 but the covering is here narrow, leaving anteriorly 

 two extensive, but not deep, uncovered fossae, as seen 

 at Fig. 2102, over the back of which the bone 

 stretches like a bridge. The articulating single 

 condyle is very prominent, and just above it (Fig. 

 210.^) is the cerebral cavity. 



The limbs of tortoises differ remarkably, from an 

 elephantine club-foot, with the strong claws only 

 apparent, to feet divided and webbed, and so on to 

 limbs formed into large undivided paddles, by means 

 of which the species wing their way in the rolling 

 ocean, as birds through the regions of air. 



The motions of ordinary tortoises on land are 

 proverbially slow : they hobble along, with an awk- 

 ward irregular gait, on their ill-shaped club-feet, and 

 seem with all their toil to make but little way ; they 

 do not put the sole fairly to the ground, but rest 

 upon the edge, which is furnished with horny la- 

 minae, tubercles, or hoof-like nails. Ill-provided as 

 they may appear to be for the work of burrowing, 

 yet they excavate pits with unexpected facility, 

 and by dint of labour contrive to bury them- 

 selves in the soft ground, scraping up the earth with 

 the fore-feet, and throwing it behind with the poste- 

 rior pair. Hybernation appears to be general 

 among the terrestrial species. 



Tortoises eat slowly and deliberately, and we have 

 seen them, when at work on their vegetable food, 

 place their fore-limbs upon it, so as to press it to 

 the ground, when, having seized a portion between 

 the jaws, they separate it by drawing the head rapidly 

 backwards. 



These animals, as is well known, endure long fast- 

 ing with impunity, and are extremely tenacious of 

 life, surviving for days, or even weeks, the severest 

 wounds and mutilations. We shall not enter into 



