REPTILIA. 



269 



different genera, and even in different species. 

 It generally consists of a body or centrum, 

 which is sometimes itself divided into several 

 pieces, and of two and sometimes three pairs 

 of cornua ; also under the anterior part of its 

 body there is suspended a bone or a cartilage 

 (sometimes double) which is the special bone 

 of the tongue, the analogue of the lingual 

 bone of birds, only in them it is articu- 

 lated in front of the body of the hyoid bone, 

 whilst in the Chelonians it is suspended under- 

 neath. 



The greater cornua (the anterior pair, when 

 only two pairs are present, the middle pair 

 when there are three, that which represents 

 the styloid bones) embrace the oesophagus, 

 and 'mount up behind those muscles which 

 represent the digastric or depressors of the 

 lower jaw, but without being attached other- 

 wise than by their own muscles. 



In Trionyx, the body of the os hyoides, 

 is composed anteriorly of a cartilaginous point, 

 beneath which is suspended a large lingual 

 cartilage of an oval form, At the base of 

 each pointed cartilage there is attached an 

 osseous piece of a rhomboidal shape, which 

 represents the anterior cornua; behind this 

 are four other pieces, forming a disc, which is 

 concave superiorly, broadest in front, and 

 deeply notched both posteriorly and on each 

 side. To the anterior angles of this disc are 

 appended the middle cornua and to the pos- 

 terior the posterior cornua. All four of these 

 cornua are considerably ossified. The middle 

 cornua consist of one long piece, which is 

 compressed, of an arched form, and termi- 

 nated by a little cartilage. The other cornua 

 are broader and flatter ; they are eked out 

 by a cartilage, in the thickness of which are 

 enclosed five or six osseous nuclei, all placed 

 in a line with each other, each of a round or 

 oval form, and quite hard and distinct, so 

 that the os hyoides of this reptile seems to 

 consist of twenty different osseous pieces, 

 which apparently remain distinct through life. 



The hyoid apparatus of Chelys is equally 

 remarkable. Its body is composed of a single 

 long narrow piece, of a prismatic shape, hol- 

 lowed above into a canal in which the trachea 

 is lodged. Anteriorly, this central portion ex- 

 pands in order to sustain two additional pieces 

 on each side, four in all, without reckoning 

 the centrum itself. The two middle ones 

 unite in front, leaving a space between them- 

 selves and the principal body, which is closed 

 by a membrane upon which the larynx reposes. 



The two lateral pieces perhaps represent 

 the anterior cornua ; it is at the dilatation 

 that they form with the expanded portion of 

 the centrum that the middle cornua are ar- 

 ticulated : these are very strong and prismatic 

 for the internal half of their course ; afterwards 

 slender ; and they give attachment externally 

 to an additional piece, which is distinct from 

 the rest of the cornua. 



The posterior cornua are articulated to the 

 posterior extremity of the prismatic portion 

 of the centrum; they are long, slightly com- 

 pressed, and curved. Under the anterior and 



dilated portion is suspended the lingual bone, 

 which consists anteriorly of a semicircular 

 cartilage, and behind of two crescent-shaped 

 osseous pieces, the inner angle of which is 

 prolonged into a kind of tail or pedicle that 

 passes beneath the prismatic body of the 

 hyoid bone. 



In the turtles, the body of the hyoid re- 

 sembles an oblong shield, concave upon its 

 upper surface for the sake of lodging the 

 larynx and the commencement of the trachea ; 

 pointed in front, where it forms part of the 

 tongue, laying above the lingual bone. The 

 anterior cornua are very small; the great 

 cornua are articulated to 'the middle of its 

 lateral margin, and have at their free termi- 

 nations additional cartilaginous pieces. The 

 posterior cornua are attached to the posterior 

 angles. 



The pelvis of lizards (Jig. 184.) is composed 



is. 184-. 



Pelvis of Crocodile, 

 a, ileum ; b, ischium ; c, pubis. 



of three bones, which, as in quadrupeds, assist 

 in the construction of the colyloid cavity. The 

 os ilii (a) occupies the upper half; its neck 

 is broad and short, and its spinous portion, 

 instead of running forwards, as in mammifers, 

 or being rounded, as in the crocodile, is di- 

 rected obliquely backwards, in the shape of a 

 narrow band. 



Inferiorly, the pubis (b) and the ischium (c) 

 are conjoined with their fellows of the 

 opposite side along the mesial line ; but the 

 pubis does not unite with the ischium, and 

 consequently the two infra-pubic foramina 

 are only separated from each other by a liga- 

 ment. 



The pelvis of the different genera of lizards 

 are principally distinguished from each other 

 by the symphysis of the pubic bones, which 

 in the monitors is formed by the junction of 

 two broad truncated surfaces; but in most 

 other genera by a much less extensive union. 

 The junction between the ossa ischii is always 

 effected by a wide surface. 



The chameleon differs from all other lizards 

 in having the ossa ilii straight, and directed 

 almost perpendicularly upwards, to be at- 

 tached to the spine. They are likewise re- 



