REPTILES. 



the hyoideal cartilage' lias a triangular figure : the two pof- 

 terior angles are elongated to form the cornua. 



The OS hyoides forms a broad nearly fquare plate, im- 

 mediately applied to the inferior parietes of the palate and 

 back of the mouth, in all the batracians, except the fala- 

 manders. The anterior cornua go off towards the front 

 from the anterior angles, feparate more widely before they 

 turn backwards, then are continued towards the angle of 

 the jaw, and curved from below upwards, in front of this 

 angle, to be fixed to the poflerior part of the cranium. 

 The pofterior horns are Itraight, ilrong, bony, not confo- 

 lidated with the fquare plate, but articulated to its pofterior 

 angles, and direfted obliquely backwards and outwards. 

 The larynx is placed between them. The hyoid cartilage of 

 the falamanders has a triangular form : the corr.ua go off from 

 the pofterior angles, and afcend at the fidt-s of the neck. 

 Their pofterior edge is confolidatcd to a thread of the 

 fame nature, bent in the form of a handle, and having its 

 acterior extremity united to that of the oppofite thread in 

 the middle of the pofterior concavity of the hyoid cartilage. 

 On each fide of the branches of this cartilage, towards tlie 

 front, there is a broad cartilaginous plate, nearly parallel 

 to them, and only joined by mufcles which go from one to 

 the other. It feemsto hold the place of an anterior horn. 



In the thirty-fourth plate of the fifth volume of the 

 Legons d'Anat. comparee, there are figures of the os hyoides 

 of the iguana, the Nilotic crocodile, the Nilotic tupinambis, 

 the lacerta agilis, the gecko fimbriatus, aiiiphifbtena, an- 

 other ferpent, the teitudo grasca, the falamander and frog. 



Mufcles of the Os Hyoides In thofe faurians, which have 



a more or lefs protraftile tongue, theie mufcles contribute 

 greatly to its elongation, by carrying the bone forwards. 



We find in reptiles ; ift, a mufcle analogous to the mylo- 

 hyoideus. It is compofed, in the two firft orders, of feveral 

 portiors; vi%. an intermaxillary, fixed to the lower edge 

 and internal furface of the branches of the lower jaw ; a 

 fecond very thick, afcending behind each angle of the jaw, 

 upon the digaftricus, and attached to the occiput ; a third 

 pafling to different diftances in the neck, fixed to the fliin 

 above, and embracing the neck like a girth. It is analo- 

 gous to the cutaneus colli ; and embraces the whole extent 

 of the neck in the chelonians. In the common iguana the 

 intermaxillary portion does not extend to the arch of the 

 chin ; and in the gecko there is only a thin aponeurofis 

 reaching fo far. But, in general, the mylo-hyoideus is fixed 

 to the OS hyoides in thefe two orders, which is not the cafe 

 in the batracians ; in which the mufcle feems to exift merely 

 for the purpofe of filling the wide interval between the 

 maxillary branches, and fupporting and elevating the parts 

 above it. Its fibres are direfted tranfverfely from one 

 branch to the other ; they are divided in feveral fpecies by 

 a median line, and attached to the internal furface of the 

 maxillary branches, which enables them to elevate more 

 advantageoufly the fubjacent parts. In the rana ocellata the 

 pofterior edge is feparated on each fide, to afcend within 

 the angle of the lower jaw as high as the palatine membrane. 



2. The mufcle analogous to the flerno-hyoideus is at- 

 tached in the chelonians, between tlie two cornua of the fame 

 fide, and to the pofterior cornu ; it defcends along the 

 neck, paffes within the firft bone of the fhoulder, and is 

 inferted on the infide of the neck of the fecond bone. It 

 refts, in this courfe, againft the fides of the cefophagus, 

 and is Itrongly attached to the pharynx towards its anterior 

 extremity. 



The fame mufcle, in the faurians, is attached on the out- 

 fide of the fternum, between the fterno-maitoidei, and is 

 filled to the pofterior cornu of the hyoid cartilage. In the 



iguana, it is fixed to nearly the whole pofterior edge of tlie 

 firft part of thefe cornua ; in the gecko fimbriatus, to t^ie 

 middle of this edge. In the caiman, after toucjiing the os 

 hyoides, it is continued to the lower jaw, and inferted far 

 back in its lower edge. 



It is much elongated in the cameleon, and carried far 

 backwards on the outfide of the fternum, /orming a point 

 in the fame direction. This mufcle covers another, thinner 

 and broader, but of the fame length, equally contiguous to 

 its fellow of the oppofite fide in the two pofterior thirds, 

 and inferted in the extremity of the pofterior cornua of the 

 OS hyoides. It might be named fterno-ceratoideus. In the 

 agame umbra (iguana umbra, Linn.), the fame mufcle ex- 

 tends equally backwards on the outfide of the fternum. 

 The fterno-hyoideus has two portions in the crocodiles, 

 which are only feparated beyond the fternum : the lower 

 one is thinneft, and inferted in the edge of the hyoid plate ; 

 the outer, broader and thicker, reaches the pofterior edge 

 of the cornu, and after a flight tendinous interfeftion, 

 which ferves to attach it to this cornu, is continued in the 

 fame dircdlion to the jaw, and forms the firft layer of the 

 cerato-maxillary mufcle. 



In the ferpents, the place of the fterno-hyoideus is fup- 

 plied by a cofto-maxillary mufcle, extending from the an- 

 terior ribs to the lower jaw. Its internal fibres go from the 

 jaw and the ribs to the hyoid cartilage. 



It is prolonged, in the batracians, except the falamanders, 

 within the fternum, to the fartheft end of this bone, where it 

 is fixed ; or it only reaches the middle of the fternum. Many 

 of its fibres are expanded on the pleura. In front it is di- 

 vided into feveral portions, inferted fucceffively in the ex-- 

 ternal edge of the hyoid plate. One of thefe goes as far as 

 the anterior cornua, and is fined to it by a flender tendon. 

 In the falamanders, the fterno-hyoideus is continuous with 

 the reftus abdominis, and partakes in its motions. 



3. The omo-hyoideus does not exift in the ophidians. 



In the chelonians it ends in the ftieath of the mylo-hoideus, 

 which inclofes the extremities of the anterior cornua of the 

 OS hyoides. This mufcle is vei-y confiderable in fome 

 faurians. In the gecko, for example, it is widened, to be 

 inferted in the greateft part of the pofterior cornua : it 

 covers the greateft pare of the fterno-hyoideus in front. 



In the iguana it is contiguous to a mufcle, which has the 

 fame direction : it is attached to the clavicle behind, and 

 above the body of the hyoid cartilage in front. In the cai- 

 man it is alfo compofed of two portions. The external, 

 which is foon detached from the following, is fixed to the 

 palatine membrane near the lower jaw. The internal is at- 

 tached to the angle of the hyoideal cornu. 



It is long and flender in the cameleon ; it pafles on the 

 outfide-of the fterno-ceratoideus, and is fixed to the body of 

 the OS hyoides, on the outfide of the fterno-hyoideus. 



The omo-hyoideus of the frog is mentioned in the account 

 of the mufcles of the ftioulder. 



4. Mufcle analogous to the ftylo-hyoideus. Tliis has 

 only been noticed in the frogs and toads. It comes from 

 the back of the head, behind the ear, where it is attached 

 at the fide of a mufcle analogous to the fterno-maftoideus. 

 It is divided into two portions in the rana ocellata, and into 

 three in the common frog : they are all attached to the pof- 

 terior cornu. 



5. The genio-hyoideus. The chelonians have only one, the 

 tendon of which is fixed to the arch of the chin : the two 

 fleftiy portions feparate as they go backwards, and are fixed 

 to the bafis of the pofterior hyoideal cornua. In feveral 

 faurians the ftrudlure is nearly the fame ; as in the common 

 iguana, and the caiman, for example. It confifts of two 



portions 



