VERTEBRATA. 



203 



FISSILIXGUIA.- Tongue slender, cleft, extensible. Eyelids pre- 

 sent, except in Ophiops. 



There are two movable eyelids, and sometimes a nictitating 

 membrane. The body is never serpent-like; and the legs are 

 always well developed. The scales are disposed in transverse 

 bands on the belly and tail ; the latter is often compressed, es- 

 pecially in the aquatic species. Some of the species attain a 

 length of seven feet ; Mosasaurus, an extinct form of the Chalk 

 formations, of seventy-five feet 



Monitor 

 Hydrosaurus. 



Ophiops. 

 Acanthodactylus. 



O-fc T\AA WOWU.A U.0 ^ , . 



Monitor = Varanus. <fbrita. 

 Heloderma. Tropidosaurus. 



Psammodromus. 



Lacertida. 

 Eremias. 



*Mosasaurus. 



XantusiidoB. 

 Xantusia. 



Ameivid<B. 

 Teius. 

 Ameiva. 

 Crocodilurus. 



STROBILOSAURA. Tongue short, fleshy, not extensible. Eyelids 

 present. Ventral scales small, rhombic, overlapping. Four well- 

 developed feet, with mostly slender unequal toes. 



Body frequently compressed, and with a row of erect pointed 

 scales on the head and back. Draco has the skin expanded at the 

 side by its six false ribs, greatly elongated, by which means it is 

 enabled to take flying leaps. 



Agarnidse are acrodont, Iguanidae pleurodont. These are 

 lizards, frequently of large size, found on trees and on rocky 

 ground. 



NYcrisAURA(=Ascalabota). Tongue short, fleshy, not exten- 

 sible. Eyelids rarely present. Toes subequal, more or less dilated, 

 the claws sometimes absent 



