KEPTILES. 



Sciences (Perrault and Duvcrney) undertook to demon- 

 llrate the falfehood of the opinion of Herodotus. Geoffroy, 

 one of the French favans, who attended the Egyptian army, 

 has given us an account of the maUer, wliicli fettles all theie 

 difputes, by provnig that the Itatement of Herodotus is al- 

 molt rigoroudy true ; and that tlie crocodile is the only 

 known animal, whofe upper jaw, inc'uding within its 

 branches the cranium, is moveable on the h)wer jaw, which 

 poiledes only an almoft infenfible degree of motion. " No- 

 thing can be more paradoxical liian the head of the croco- 

 dile : every thing which is placed laterally in other animals, 

 as the moving powers of the jaw, &c. is thrown Ijeliind. 

 The temporal bone itfelf extends backwards far behind the 

 cranium, is elongated, and transformed into a double con- 

 dyle. We have in faft nearly delcribed the crocodile's 

 head, when we fay that it confifls of two mandibles ; for the 

 cranium is fo fmall, and out of place, that it efcapes notice 

 at firlt. We find it below, and a little in front of the oc- 

 cipital criita. The brain is fo far forwards, that the eye 

 and ear are above and a little behind it. 



" The lower jaw is one-fixth longer than the upper, with 

 the cranium : it prefents a cavity with a double iurface, in 

 wiiich the condyle of the temporal bone is articulated by 

 ginglymus. The occipital condyle is in the fame line as 

 the temporal condyles : thus the head is really held at its 

 articulations, like the lid of a box by the hinge, and is con- 

 fined entirely to motions upwards and downwards. When a 

 living or fluffed animal is examintd, it is difficult to believe 

 that the head ends at the extremities of the jaws. There is 

 a regular fuUnefs of the front of the neck, which might be 

 regarded as the frontal part of tlie head : this arifes from 

 the enormous temporat mufcles, winch lie between the refti 

 and obliqui. The latter, arifing from the cervical vertebra, 

 and inferted in the occipital crifta, elevate the head upon 

 the neck, making it defcribe an arc of 45°. The fl-in be- 

 hind the occiput being thin, yields to the motions of the 

 head ; while the lower jaw, on the contrary, is inclofed in 

 a kind of (heath of hard, rugous flcin. If there were a muf- 

 cular force capable of drawing it down, this covering would 

 impede its defcent, while it is (lill further confined behind : 

 the long procefs fituated beyond its articular furface, de- 

 fcribing a curve, approaches the fkiu exaftly at the point 

 where it is armed with a long fcale, which offers an almoll 

 invincible refiftance to the elevation of the condyle, and 

 confequently to the depreffion of the jaw. Yet it is not en- 

 tirely fixed, as Marinol imagined, who itated that it forms 

 a fingle bone with the fternum. Two fmall mufcles have 

 tlie power of moving it flij^htly." (Annales du Mufeum, 

 toni. ii. p. 38, et feq. ) This defcription is accompanied 

 with an excellent figure of the flcull, in the elevated ttate of 

 the upper mandible. An analogous figure or the whole 

 head is given by Humboldt, Recueil d'Obf. de Zool. &. 

 d'Anat. comparee, torn. i. pi. 4. From the figures of the 

 Nilotic crocodile, in Blumenbach's Abbildungen Natur 

 Hillorifcher gegenft'ande, N° 26 ; and of the St. Domingo 

 crocodile, in the Annales du Muf. torn. ii. it appears, that 

 the animal mod frequently exhibits this elevation of the 

 upper jaw. It cannot be necelTary to point out how the 

 raifing of the entire cranium and fuperior mandible, jull de- 

 fcribed, differs from the motion of the upper jaw upon the 

 craniun: : this has been already done by Blumenbach. See 

 SyUem of Comparative Anatomy, p. 111, note 8. 



The length of the lower jaw is much more confiderable in 

 comparifon to that of the upper in reptiles, where it is ar- 

 ticulated far back, and is even prolonged beyond its arti- 

 culation, than in mamn.-alia and fifhes, where this articulation 

 is placed more forwards. Its compofition is more compli- 



cated in the reptiles, than in any other order. In the green 

 turtle (telludo mydas) it confilts of feven diftinft pieces, a 

 middle one firming the arch, and three others on each fide, 

 forming a continuation of its branches. The fartiiefl of the 

 three penetrates like a wedge between the two others, and 

 forms a great part of the articular cavity. In many of the 

 fauriaiis the number is ftiil greater: the lower jaw of the 

 Nilotic crocodile, and of the caiman (croc, alnericaiius), has 

 no fewer than twelve pieces, arranged as follown. As the 

 two branches are diftinft, and united by a future, each of 

 them mull be compofed of fix pieces; i, one, in which all 

 the teeth arc implanted j 2, another, lying along tiie inter- 

 nal furface of the former, without reaching to its anterior 

 extremity ; 3 and 4, two others articulated with the pre- 

 ceding ; -viz,, an inferior one prolonged to the pofterior ex- 

 tremity of each branch, a fuperior extending as far back as 

 the other in the Nilotic crocodile, but not fo far m the caiman, 



5. The greatelt part of the articular cavity is excavated in 

 a fifth piece within the two former, and coiiflituting the inner 

 and fuperior part of the portion beyond that cavity. 



6. Ladly, a fixth piece forms the front and inner part of 

 the orifice of the dental canal. The lower jaw of the tupi- 

 nambis (lacerta monitor) is alio compofed of twelve pieces, 

 two of which form the coronoid procefl'es, while the other 

 ten are analogous to thofe defcribed as entering into the 

 formation of the lower jaw of crocodiles, excepting the laft. 

 There are eight or ten in mofl of the other faurians. We 

 find four in each branch in the genus anguis ; an anterior one 

 united to its correiponding piece in front, and three pofterior 

 ones joined to the former. There are only four altogether 

 in the amphifbxna. Tlie two lafl mentioned generaare the 

 only ophidian reptiles, in which the jaws are not feparated 

 in front. In all the others there is a feparation, and each 

 branch has only two diflinft pieces ; an anterior, in which the 

 teeth are implanted, and a pollerior ; they are united by 

 future, and vary in relative length, according to the number 

 of teeth. The very open arch, compofing the lower jaw 

 of the batracian order, is made up of fix pieces ; the middle 

 of which are the moll flender. 



The anterior angle, formed by the union of the two 

 branches, depends on the form of the fiiout in general, on 

 the figure of the two branches, the prefence or abfence, 

 number and fize of the teeth. Sec. It is rounded and very 

 open in the chelonian reptiles, and more fo in the batracian. 

 In the ophidian order, which have the branches of the jaws 

 moveable, it is fufceptible of change, according as their 

 extremities are approximated or drawn afunder ; indeed in 

 the former cafe only can it be properly faid to exiil at all. 

 It is rounded in the amphifbjena ; more angular in the anguis ; 

 llill very obtufe in the geckos (lacerta gecko), which have 

 wide jaws, with the branches of the lower curved only in 

 the horizontal diredlion ; it is lefs fo in the cameleon and 

 flellio (lacerta flellio), the fcinks (lacerta fcincus), and the 

 lizards, although in all thefe the two branches are only 

 joined by their extremities. It is acute in the tupinambis and 

 iguana, in which the branches, fomewhat curved in the ver- 

 tical diredlion, are approximated for a longer fpace. The 

 Nilotic and Gangetic crocodiles differ very much in this 

 refpeci. The two branches are united in the latter in the 

 greatelt part of their extent, as in the cachalot, and confe- 

 quently form a long bill, in the edges of which the two rows 

 of teeth are implanted. In the former, on the contrary, 

 the branches remain feparate, and only approximate towards 

 their extremity, increafing a little in thicknefs at the fym- 

 phyfis. 



The portion of the bone, which is incurvated towards 



the cranium in mofl of the mammalia, and conftitutes 



4 the 



