REPTILES. 



The Ih-uftiire of the cranium of tortoifes btars more 

 rcfemblance to that of crocodiles than of frogs. The 

 frontal bones form only the roof of the orbits, and the cra- 

 nium does not pafs between thefe cavities. They are very 

 (hort/ and the parietalia are three times longer. The latter 

 are not confined to covering the cranium. They extend on 

 each fide, and form an arch over the temporal fofi'a. In the 

 fea tortoifes this arch is completed by two peculiar bones, 

 which extend from the os parietale to the zygoma, and the 

 anterior of which bounds the orbit behind. 



The articular procelles are direfted downward, as in the 

 camcleon. Above thefe and the meatus auditorius, we find 

 confiderable maftoid procefles, which are pointed fuperiorly 

 in land tortoifes, but are rounded and marked by a longitu- 

 dinal furrow in the fea tortoifes. 



Serpents have two frontal bones almoft fquare, and a 

 fingle parietal bone. Their cranium advances forward be- 

 tween the orbits, as in frogs. The occipital bone.has a 

 procefs direded backward, and connefted with a particular 

 moveable bone, analogous to the fquare bones of birds, to 

 which the lovi^er jaw, and the arches which form the upper, 

 are articulated. 



The general form of the cavity of the cranium of reptiles 

 is oblong, and almoft of an equal breadth, being merely a 

 little contrafted between the ears. The tortoife has a kind 

 of fella turcica, the four clinoid procefles cJf which are 

 dire&ed forward. The fphenoidal foffa is fomewhat depreded 

 in the ferpents, but it has no clinoid procefles. It is a femi- 

 lunar depreflion, the plane of which is fituated from before 

 backwards. 



The bafilar foffa is lower than the other foH;e in the croco- 

 dile, and in fome tortoifes. 



Foramina of the Cranium. — The interior part of the cra- 

 nium is frequently not clofed by offification in reptiles and 

 fifties, and the olfaAory nerves pafs through a large vacant 

 fpace, which is not fubdivided into particular holes. This at 

 leaft is the cafe with the cameleon, the iguana, tortoifes, 

 the pike, the anarrhichas, &c. In others, the olfaftory hole is 

 contrafted, but is ftill fimple, as in the crocodile. It is double 

 in frogs and falamanders. The rays and the fliarks have alfo 

 two holes, which are confiderably removed from each 

 other. 



The optic holes are likewife fometimes united into one, as 

 in the crocodile : thofe of the tortoife are much removed 

 from each other, and are diftinguifhed from the great hole 

 in the front of the cranium, by only a fmall bony partition. 

 The ftrufture of the cranium in the pike is fimilar. In the 

 frogs, the rays, the anarrhichas, and it Ihould feem in the 

 greater number of fifties, the optic holes are at a great diftance 

 from each other, and perforate the fides of the cranium. 

 Thefe animals have no fpheno-orbitar fiffure, and the fmall 

 nerves tranfmitted to the eyes pafs each through a particular 

 foramen. 



There is, in general, only one hole on each fide for the three 

 branches of the fifth pair of nerves, which, therefore, fup- 

 plies the place of the foramen rotundum, foramen ovale, and 

 in part of the fpheno-orbitar fifture. This hole, however, is 

 divided into three in the carp. 



The meatus auditorius internus exifts in reptiles. 

 The Face. — In the crocodile the face refembles one-half 

 of a cone irregularly flattened on its convex furface. It is 

 chiefly formed by two oll'a maxiUaria, and two ofla nafi, 

 which are fituated almoft parallel to each other, and two 

 ofla intermaxillaria, which form the end of the muzzle, and 

 furround tbe aperture of the nofe like a ring. 



The bones analogous to the lacrymalia are four in num- 

 ber, two on each fide. The os mals, which is very large, 



after forming the inferior, and affording a fmall procefs 

 to the pofterior edge of the orbit, extendi direftly back- 

 wards to join the great maftoid protuberance : thus the 

 temporal fofla has no communication outwardly; ex- 

 cept by a hole which is fmallcr than the orbit, and the 

 greater part of which is covered by thefe bones, as by an 

 arch. 



The nafal foflse are continued in a long and narrow tube 

 under the foramen magnum. They perforate the ofla pa- 

 lati, and a particular bone which is analogous to the 

 pterygoid proceffes of the os fphenoides. This bone is fi- 

 tuated almoft precifely under the cranium, and is enlarged 

 on each fide until it forms a kind of fquare and almoft 

 horizontal wing. An offeous branch unites it laterally to 

 the OS maxillare and os malae, in fuch a manner that a large 

 hole is left on each fide of the arch of the palate. 



In the cameleon the face is concave fuperiorly, and 

 bordered by a ferrated ridge tlwoughout the whole of its 

 circumference. We obferve two holes which communicate 

 with the orbits, and two other oval foramina, which cor- 

 refpond to the incifive holes in the palatine furface. The 

 bones which compofe the face are nearly the fame as thofe 

 of the crocodile. The other lizards exhibit ftill lefs dif- 

 ference. 



The frog and the falamander have the nafal and inter- 

 maxillary bones very fliort, and broader than long, which 

 renders their face round anteriorly. The os maxillare is 

 very narrow, aiid is fcarcely contrafted in forming the 

 zygomatic arch. The orbits are large, but have no in- 

 ferior furface, and therefore communicate with the palatine 

 foffa. The offa palati form the anterior edge of the or- 

 bitar fofla inferiorly. They refemble portions of a circle. 

 They are furnifhed with pointed teeth on their circumfer- 

 ence. The canal of the nares is very fhort in the jfala- 

 mander. There is only a fimple hole in the frog. 



The face of the Surinam toad is very flat, but the bones 

 are the fame as in the frog. The orbitar foffae are oval, 

 and no aperture fimilar to the canal of the nares can be 

 diftinguifhed. 



The face of ferpents is rounded nearly in the fame man- 

 ner as that of lizards. Between the os frontis and os 

 parietale, there is a particular bone which terminates the 

 frame of the orbit pofteriorly. Thefe animals have no os 

 malas. We can, however, eafily diftinguifh two offa nafi, 

 two offa maxiUaria fuperiora, two offa intermaxillaria, and 

 fome analogous to the palatini" arches of birds, which are 

 furnifhed with teeth, and which are articulated to the bone 

 which fupplies the place of the os quadratum, with refpeft 

 to the lower jaw. Two particular bones unite thefe arches 

 to the maxiUaria fuperiora. 



In thofe that have teeth, or poifonous hooks, as the 

 viper, the rattlefnake, &c. there are befides two fmall 

 peculiar bones, articulated and moveable, which fupport 

 thofe teeth. They are fituated upon the intermaxillary 

 bones and the anterior extremity of the offeous branch, 

 which joins the fuperior maxillary bone to the arch of the 

 palate. 



The face of the tortoife is circular before, and rounded 

 on every fide. It is compofed of nearly the fame bones 

 as that of the crocodile. The intermaxillary bones are, 

 at a very early period, confolidated with thofe of the upper 

 jaw. The bones analogous to the os mala: are three in num- 

 ber, one articulates with the os temporum and with the 

 two others ; it is fituated pofteriorly, and forms the zygo- 

 matic arch. The other two portions are received on its 

 anterior extremity ; one extends upwards, and unites with 

 the orbitar angle of the os frontis ; the other is direfted 

 7 downward, 



