110 



COMPARATIVE ANATOMY 



The cranial bones (Figs. 80-86) are much more numerous and 

 varied in form than in recent Amphibia. The solid base of the 

 skull is formed by bones developed on a cartilaginous foundation, 

 viz., of a basioccipital and a basisphenoid, on which latter there 

 may be a lasipterygoid process on either side for articulation with 

 the pterygoid bone. An alisphenoid ossification may be present ; 

 presphenoids and orbitosphenoids are usually wanting. The 



Bctochoa/nal cart. 



Paraseptal curt. 



lasiptg. proc 



Parasph 



Perilympli. jo,: 



Post, basieran. fontantlle 0<\ con<L 

 FIG. 80, B. 



parasphenoid, which plays so important a part in the Anamnia 

 as an investing bone on the roof of the mouth, undergoes a 

 gradual reduction, but can still be recognised, although more or 

 less included within the basisphenoid : it may be represented by 

 lasitemporal ossifications which unite with the latter bone, and 

 its anterior part may form a l/asisphenoidal rostrum. Above the 



