224 



CHARACTERS OF VERTEBRATE ANIMALS 



external trace of limbs, though vestiges of these are present in 

 some of its relatives (see fig. 139), and its teeth are slender and 

 fang-like. Its food consists of slugs, worms, insects, and the like. 

 The specific name " fragilis " has reference to the readiness with 

 which the tail breaks off when the animal is handled or struck, 

 a protective arrangement not uncommon among lizards (p. 194). 



6. Venomous Lizards are represented only by one genus 

 containing two species, both North American, one being from 

 Mexico {^Heloderma horridd) and the other from Arizona {H. 

 suspectd). They are carnivorous forms of considerable size, 

 coloured and mottled in such a way as to make them conspicuous 

 objects when seen apart from their natural surroundings. The 

 poison arrangement is something like that found in snakes, there 

 being slender fang-like teeth grooved to conduct a poisonous fluid 

 from glands at their bases. 



7. Monitors are the largest living lizards, and are distributed 

 over the warmer parts of the Old World. In general proportions 



Fig. 140.— The Nile Monitor [Varanus NUoiicus) 



they are not unlike the typical form previously described, with 

 which also they agree in the possession of a well-developed 

 forked tongue capable of being thrust far out of the mouth. A 

 common species is the Nile Monitor {Varanus Niloticus), which 



