218 



THE ANATOMY OF YERTEBRATED ANIMALS. 



I'N 



Fig. 77.— Longitudinal and vertical section of the hinder part of the skull of a CrotXfdila 

 Eu^ Eustachian tube : P jV, posterior nares ; P, pituitary fossa. 



2. All the bones of tlie skull (except the mandible, stapes, 

 and hyoid) are firmly united by sutures, which persist through- 

 out life. 



3. There are large parotic processes. Both the upper and 

 the lower temporal arcades are completely ossified, and formed 

 by post-frontal, squamosal, jugal, and quadrate- jugal bones; 

 supra-temporal, lateral-temporal, and post-temporal fossa3 are 

 formed, as in the Lacert'dia^ though their relative sizes are 

 very different. 



4. The maxillary and the palatine bones develop palatine 

 plates, which unite suturally in the middle line, and separate 

 the nasal passages from the cavity of the mouth, as in Mam- 

 9nalia / and in all existing Crocodiles, but not in IHeosauriis 

 or JBelodon^ the pterygoids are also modified in tlie same way 

 (as in Mymercophaga among Mammals), so that the posterior 

 nares are situated very far back beneath the base of the skull. 



5. In consequence of the development of these palatine 

 plates of the maxillary and palatine bones, the two vomers 

 are, in most Crocodiles, invisible upon the under-surface of 

 the bony roof of the mouth. 



