REPTILES. 



the nfccndin;^ branch of the jaw, iloes not exift in rep- 

 tiles. 



Molions of the Jciivs. — Reptiles may be divided into two 

 orders, according to the conformation of their maxillary 

 bones, and the kind of motion of which they are fufceptible. 

 In the firll would be placed thofe which have the lovver jaw 

 only moveable, as the li/.ards, tiie telhidincs (tortoife and 

 turtle), the frogs, the falamanders, and the genera aiiguis 

 and amphiiba-na among the ferpents. The fccond would in- 

 clude the colubres, and the venomous ferpents, which cnn 

 move both jaws. 



The general difpofition of the articulation is nearly the 

 fame in reptiles as in birds (fee Bihds, in Comparative Ana- 

 tomy). Inftead of a condyle at the pollerior extremity of 

 the iawj an articular furface is excavated to receive an emi- 

 nence bearing conllderable analogy to the os quadratum of 

 birds, and differing from it only in not being fo moveable ; 

 often, indeed, it is only a fimple prolongation of the tem- 

 poral bone. To this mod inferior point of the cranium, 

 and to an articular furface nearly tranfvcrfe in its direftion, 

 and (haped like a condyle, the lower jaw is articulated by a 

 glenoid cavity, of which the middle part fometimes prefents 

 a rifmg line, converting it into a kind ot pulley. Behind 

 this articular cavity there is often a more or lefs confider- 

 able bony procefs, affording attachment to a mufcle ana- 

 logous to the digaftric. 



'^The moll remarkable differences requiring our notice here 

 are, the form of this prominence or condyle of the tem- 

 poral bone ; the greater or lefs prolongation of the procefs 

 behind the articulation ; the fituation and extent of the tem- 

 poral foffa ; and, laftly, the exiftenceor abfence of the emi- 

 nence occupying the fituation of the coronoid procefs. 



In proportion as the temporal eminence is carried back- 

 wards, the jaws approach more nearly to each other in their 

 longitudinal direftion. We fee this in the crocodile, fala- 

 mander, frog, turtle, and tortoife. When, on the contrary, 

 it defcends vertically, or very obhquely, and is very elon- 

 gated, as in the cameleon and iguana, it forms a kind of 

 pedicle to the lower jaw, which, by feparating it from the 

 cranium, produces a much more confiderable interval between 

 the jaws. Several kinds of lizards, as the lacerta agilis, 

 draco, &c. occupy the intermediate fpace between thefe 

 two extremes. 



The crocodile has the largeft procefs for the attachment 

 of the digaftricus. It is fenfibly diminifhed in the cameleon, 

 the gecko, the tupinambis, and the teftudines ; and we fee 

 nothing of it in the pipa, the toad, frog, and falamander. 



All four-footed reptiles have very deep temporal foffa; ; 

 they are united to the cavity of the orbit. In fome fpecies, 

 the two cavities are feparated in front by a bony circle, as 

 in the teftudines, the crocodile, the dragon, and the other 

 lizards ; but in the pipa, the frogs, and falamanders, there 

 is no orbital circle. 



There is, in the crocodile, a confiderable excavation on 

 each fide of the cranium, behind the orbit, terminating 

 below in the temporal foffa, and wanting in the crocodile 

 with bony eyelid (Crocod. palpebrofus, Cuvier). It is 

 bounded externally by a bone correfponding to the iqua- 

 mous portion of the temporal, which joins the lateral frontal 

 bone, and thus forms a tccond kind of zygomatic arch. 

 The fize of this excavation differs much in the different 

 fpecies. No doubt it contains mufcles. But we find no 

 exprefs and fatisfaftory defcription of it and its mufcles, 

 nor of the mufcles of the jaw in the writings of the French 

 naturalifts already quoted, on the fubjeft of the crocodiles. 

 The coronoid procefs of the lower jaw is not prominent 

 JQ reptiles. There is a mere rudiment of it in the teiludincs, 



the cameleon, and fome li/ards, at, thf iguana, but there is 

 no trace of it in the crocodile, the frogs, and falamanders. 



The mufcles of the jaw, in the oviparous quadrupeds, are 

 analogous to thofe of the mammalia, and referable them in 

 number. 



The maffeter is large and diflinft in the tupinambis, occu- 

 pying all the fpace comprifed between the polterior edge 



of the orbit and the meatus auditorius. It is direfted ob- 

 liquely from behind forwards, fo that it raifes and carries the 

 jaw backwards. This mufcle is fmall in the agame marbre 

 (lacerta marmorata), and the turtle. It is fo flender, that 

 'it can fcarcely be dilUnguifhed from the lower part of the 

 temporal. 



The temporal mufcle is very large in the turtle, occupy- 

 ing all the temporal foffa, and forming the back of the 

 orbit. It is much fmaller in the tupinambis and common 

 lizard, in which it is almoft entirely concealed by the maf- 

 feter. 



The pterygoidei are, in general, but imperfeftly diftin- 

 guidied from each other. They envelope the whole branch 

 of the jaw towards its extremity in the tupinambis ; their 

 fibres are in a manner twilled. They elevate the jaw and 

 carry it forwards ; thus they aft in an oppofite direftion to 

 the two preceding mufcles. The fame mufcles are flat and 

 thill in the turtle ; their fibres are nearly tranfverfe, fo that 

 they can move the lower jaw more direftly from fide to fide. . 



In all thefe reptiles the mufcle analogous to the digaftric 

 is flat and triangular ; the broad portion is fixed to the cer- 

 vical ligament behind the occiput, and the point terminates 

 at the extremity of the jaw, behind its articulation, and near 

 the pterygoid mufcles. 



After defcribing the mufcles employed in moving the jaws 

 of the turtle, Perrault aiferts, in his " Memoires fur les Ani- 

 maux," that it has more power in its jaws than moft other 

 animals, that it can cut very hard and flrong fubftances, and 

 that the head of a fmall turtle has been feen, half an hour 

 after it was cut off, to flrike its jaw^s together with a noife 

 like that of caflagnettes. Daudin relates the following cir- 

 cumftance, communicated to him by a Dutch naturalifl, who 

 refided feveral years in India. " When we landed in Table 

 bay, we took feveral hawk's-bill turtles (tcftudo imbricata), 

 whofe flomachs were filled with marine plants, and thick 

 fhells, which they eafily break down with their horny gums. 

 Three, which could not be brought on board, were tied to 

 the trunk of a tree, with a thick cable, but when the failors 

 returned on the following morning, they found that thefe 

 turtles had contrived to turn over on their bellies, and had 

 then cut, with their gums, the cables with which they had 

 been faftened." Hill. Nat. des Reptiles, in the edition of 

 Buffon, by Sonnini, t. i. introduftion, p. 38. 



The two jaws are not moveable in all the ferpents. They 

 may be divided into three orders. I. Thofe with the 

 branches of the lower jaw confolidated, and confe- 

 quently not pofleffing any power of thrufting forward the 

 upper jaw, or moving it laterally. 2. Thofe with the 

 branches diftinft, and united in the recent ftate by an elaflic 

 ligament. There are two modifications of the latter ; they 

 may either have merely the power of feparating the two 

 jaws ; or they may, at the fame time, feparate the jaws, 

 and carry forwards a part, or the whole of the upper. We 

 fhall fpeak of the motions of the jaws according to this divi- 

 fion, firfl defcribing the bones, and then the mufcles. 



The Bones. — In the ferpents, with the lower jaw confoli- 

 dated, the head is fhaped nearly as in the hzards. This is 

 the cafe in the anguis and amphilbma, the csecilia, acro- 

 chordus, and hydrophis. In the genus anguis the head very 

 clofely relerables that of the iguana. The arch of the upper 



jaw 



