REPTILIA. 



445 



protrude from between the carapace and plastron. The 

 skull shows the bones all immovably fixed. There are no 

 teeth, their functions being performed by sharp horny ridges. 

 All Chelonia are herbivorous. 



The tortoises are terrestrial and have a convex carapace. 

 The turtles are aquatic and the carapace is more flat, often 

 comparatively soft or leathery in texture. Many turtles are 

 truly pelagic. 



Fig. 315. — Dorsal View of a Crocodile's Skull x^ {Adnat.) 



Premaxilla. 



External Nares. 



.Squamosal. 



Quadrate. 



Note the pitted bones, the wide "gape" from the two quadrates, 

 and the pre- and post-frontal bones. 



Order N. — Crocodilia, 



The crocodiles are in many respects the most highly 

 organised of reptiles. They have an exoskeleton of bony 

 scutes covered by epidermic scales. Both limbs are 

 present and the skull-bones are immovable. 



