88 



COMPARATIVE ANATOMY 



encircles the whole skull in this region and is perforated by the 

 olfactory nerves. 



In the adult the bones are not so numerous as in XJrodeles, and 

 the frontal and parietal of either side as a rule fuse together, thus 

 giving rise to a fronto-parietal. The maxillary bar grows back- 

 wards much further than in XJrodeles, and becomes connected with 

 the suspensorium by means of a small intermediate bone, the quad- 

 ratojugal (Fig. 69). The maxillary arch is therefore complete, as 



in Tylototriton amongst 

 XJrodeles (p. 85). The 

 palatoquadrate is united 

 anteriorly with the carti- 

 laginous nasal capsule. 

 (For the relations of 

 the bones bounding the 

 mouth-cavity compare 

 Fig.69.) The bones of the 

 lower jaw are a dentary 

 and an angular, the distal 

 end of Meckel's cartil- 

 age ossifying as a small 

 " mentomeckelian." 



There is a much 

 greater reduction of the 

 branchial skeleton at the 

 close of larval life than 

 in XJrodeles. In the 

 larva representatives of 

 the hyoid and of four 

 branchial arches can be 

 recognised, but these are 

 all fused together and 

 form a continuous struc- 

 ture, reminding one of 

 the branchial basket- 

 work of the Lamprey. 

 In the adult this be- 

 comes greatly reduced, 

 and the apparatus con- 

 sists of a broad cartilaginous plate in the floor of the mouth, with 

 long anterior and shorter posterior (thyro-hyal) cornua, the latter 

 of which become ossified. 



D. Reptiles. 



Although as regards the structure of the skull existing Reptiles 

 and Amphibians are widely separated from one another, certain 

 resemblances exist between their extinct representatives {e.g., 

 Paleeohatteria and the Stegocephala). 



Fig. 70. — Hyobkanchial Skeleton of Larval 



(A) AND Adult (B) Frog. 



(After CTaupp. ) 



Z)-s, body of the hyoid ; a.c, anterior cornua ; 



2h c, posterior cornua. 



