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 SKULLx}. (4d nat.) 
Premasilla }-—External Nares. 
Mazxilla. 
Nasal. J 
Lacrymal. 
... Prefrontal. 
Orbit. 
Jugal. —.Frontal. 
Post- 
Lateral frontal. 
Temporal. 
Fossa. 
Quadrato- & 
jugal. 
Squamosal, 
Quadrate. a! 
a 2 
So oc fa 
al 
gd_> 2 
2888. 8 
dO 26 
oy Bc) aa 
ge 8 
ZS 
n fe) 
Note the pitted bones, the wide ‘‘ gape” from the two quadrates, 
and the pre- and post-frontal bones. 
ORDER V.— Crocodilta. 
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. . 
