REPTILES. 



downward, and articulates with the poftcrior and external 

 procefs of tlic os maxillare luperius. 



The ofla palati are broad, and form the pollerlor arch 

 of the nafal fod'a. 



The bones of the face of tortoifes commonly cover eacji 

 other at their edges, which are refin; J into thin lamince. 

 It is therefore very difficult to dittincruifh the futures. 



In the fea tortoifes the temporal foffx, which are very 

 deep, are covered by an ofleous lamina, which forms a 

 very folid arch above them. 



The defcription of the jaws, and the temporal foffa", is 

 given at the beginning, of the account of the digeltive 

 organs. 



Cav'tlies of the Face. — I. Nafal Ca-vlty. It is a broad 

 fpace in the tortoifes, occupying the whole thicknefs of the 

 fnout in front of the eyes, and very (hort from before 

 backwards. Its front opening is large, and nearly (quare, 

 with its plane but little inclined ; furrounded by fix bonec. 

 There are two round openings behind, corrcfponding 

 nearly to the middle of the palate. 



In the crocodile it is a long and narrow canal, extending 

 from the end of the fnout under the occiput : its bony 

 opening, formed entirely in the two intermaxillary bones, 

 is turned upwards. 



Other lizards have the nafal apertures fituated nearly as 

 in birds : that is, the front or outer on tlie fide of the fnout, 

 ^nd the hack or inner in the middle of the palate. They 

 are flill fliorter in the frogs. 



2. The orbit is never feparated from the temporal 

 fofla in reptiles by a partition, but merely by a bony 

 branch ; and even this is complete only in the lizards and 

 tortoifes, not in the frogs, falamanders, or ferpents. The 

 plane of its margin is lateral in the tortoifes, ferpents, 

 and cameleon ; it is more or lefs direfted upvv-ards in the 

 crocodile, falamanders, and frogs. The figure varies from 

 circular to triangular. Tiie inferior furface or floor is never 

 complete : either it is altogether deficient, or it is perfo- 

 rated by a very large aperture. The fame remarks are ap- 

 plicable to the inter-orbitar feptum. 



The zygomatic follae are fpoken of in the defcription 

 of the jaws and their movements, under the divifion of 

 Organs of the Vital FunSlom. 



Foram'ma of the Face. — Wliere there is no diitinftion be- 

 tween the orbit and temporal foffa, the fpheno-maxillary 

 fiflure is of courfe wanting. There are no internal orbitary 

 holes, as the relation between the orbits and nofe is alto- 

 gether different from what is obferved in the mammalia. 



The crocodile, frog, and falamander, poflefs a large 

 foramen incifivuni. The tortoife has two fmall ones : the 

 ftrufture of the lizards is not known. 



There is no fuborbital opening, reptiles having no lips 

 to receive the artery and nerve, which it tranfmits in the 

 mammalia. 



The fpheno-palatine canal appears as a finiple hole in the 

 OS palati. 



Motions of the Hear!. — The articulation of the head of 

 reptiles is confiderably behind, but the motions vary in dif- 

 ferent fpecies. 



In the crocodile there is only one condyle, fituated at 

 the under fide of the foramen magnum : the atlas is formed 

 of two portions ; the pofterior is fhaped like the fegment 

 of a ring ; the anterior, which is thicker, receives the 

 condyle, and is articulated to the fccond vertebra : there 

 are two lateral procelfes, long, fl.it, and turned backward, 

 which fupply the place of tranfverie procefles. 



The odontoid procefs of the fecond vertebra is fliort and 

 thick ; it is articulated within a cavity in the body of the 



atlas. This fecond vertebra has tranfverfe proccfTes fimilar 

 to thofe of the fird. 



All other li/.ardshave nearly the fame conformation ; but 

 the condyle feems divided in two by a longitudinal fuperfi- 

 cial furrow. 



The tortoifes have llkewifc only one condyle. In the 

 land fort It is prolonged, and divided into two, as it is in 

 the lizards. In the marine fpecies it prefents three arti- 

 cular faces, like a trefoil leaf. As this condyle penetrates 

 deep into the correfpondent cavity of the atlas, the lat'-ral 

 motion of the head is much confined. The other motions 

 of the head of tiie tortoife are thofe of projection and re- 

 traftion ; they depend upon the flexion and extenfion of the 

 cervical vertebrae. 



The frog, the toad, and the falamander, have the head 

 articulated by two condyles upon the firll vertebra, which 

 is almofl: Immoveable. 



Serpents have three furfaces, in the manner of a trefoil, 

 clofe together, upon one condyle, beneath the occipital 

 foramen. The head is not more moveable on the atlas, tiian 

 the reft of the vertebrae are upon each other. 



Bones of the Spine. — The number of vertebrae, and every 

 other attribute of the fpine, are more varied in this clafs of 

 animals than in any other. 



In the tortoifes, feven vertebrx are afligned to the neck : 

 the firll is only a fingle tubercle, the annular portion of 

 which is very diilinft. The furface, by which it is arti- 

 culated with the head, is formed of three planes ; one an- 

 terior, and two lateral. The point in which they unite is 

 the moil prominent, and to this is attached a ftrong liga- 

 ment. The furface which unites it to the next vertebra is 

 a glenoid cavity ; the fecond and the following vertebrae 

 have a prominent longitudinal ridge upon the fore-part of 

 their body. The articular procefTes defcend below the 

 body : there are no fpinal procefles, except one to the fe- 

 cond vertebra, which points forward, and one to the third 

 in the form of a fimple tubercle. The two laft vertebrx, at 

 a certain age, become anchylofed. There are eight dorfal 

 vertebrae ; but they are all anchylofed, together with the 

 ribs and the back-fliell, in one immoveable piece. They 

 have, therefore, neither procefles nor articular furface^ : 

 they are all narrower in the middle than at the ends. The 

 lumbar and facral vertebrae are llkewife confolldated witk 

 the back-fliell, but thofe of the tail are free and moveable. 

 The condyle, which forms the body of thefe vertebras at its 

 articulation with the others, inclines backward, and not to- 

 wards the head, as thofe of the neck do. There are like- 

 wife upon the fore -part of the body, at its bafe, two fmall 

 tubercles ; but all the procefles of thefe vertebrae refemble 

 thofe of the mammalia. 



In the family of lizards, the crocodile has feven cervical 

 vertebrx, dillindl indeed, but fo clofely articulated as not 

 to be moveable. The procefles are fo numerous, long, and 

 clofe, that the animal cannot bend its neck, and the cervical 

 column may, therefore, be regarded as a fingle piece. This 

 correfponds with the reports of travellers, that the crocodile 

 is unable to turn his head round. The anterior furface of 

 the body is concave, and the pofterior convex, throughout 

 the vertebral column of the crocodile. The atlas is com- 

 pofed of fix pieces, which appear to continue feparate 

 through life : the vertebra dentata has five only. The 

 other cervical vertebrx have on each fide two /hort tranf- 

 verfe procefles, which ferve to fupport the fmall ribs or 

 appendices, which limit the flexion of the neck. Each has 

 two pedicles, attached to the two procefles juft mentioned : 

 the appendix projects into a ftiarp procefs before and be- 

 hind, which touch thefe of the contiguous vertebras. The 



five 



