94 REPTILES OF THE WORLD 



great family Iguanidce (pleurodont), of the New 

 World, from the equally large family Agamidce (aero- 

 dont) of the Old World, for the external characters 

 would lead us to directly associate one family with 

 another — even discuss the close relationship of different 

 genera, as for most of the distinctly freak genera of 

 the Iguanidce we find forms of similar outlines in the 

 Agamidce. 



The teeth of lizards may be conical or flat, straight 

 or recurved, sharply pointed or terminating in queer ly 

 serrated fashion that makes each tooth look like a "bit'* 

 of some fancy drill. Among the vast aggregation of 

 lacertilians , only two are known to be poisonous; these 

 are the species of Heloderma — the Beaded Lizards, in- 

 habiting the deserts of the southwestern portion of the 

 United States, besides the arid regions of southern 

 Mexico and northern Central America. The species 

 are pleurodont; the teeth of the lower jaw are stout, 

 slightly recurved and each is provided with a venom- 

 conducting groove. In Borneo is a lizard technically 

 known as Lanthanotus borneensis; its teeth have been 

 alleged to be grooved, like Heloderma. Not much is 

 known about this creature. Notwithstanding an appar- 

 ent relationship to Heloderma, it would be unjust to 

 describe the species as in any way venomous. 



The Tail: For purposes of defense, the tail is an in- 

 valuable organ. With it, the larger lizards deal lashing, 

 whip-like blows. Many lizards have a tail of extraor- 

 dinary length — four or five times as long as the com- 

 bined length of the head and body; a number possess 

 a diminutive, stumpy appendage. With the majority 

 of lacertilians the tail is readily discarded, and it is soon 

 reproduced. Let us take one of the extremes of caudal 

 development as an illustration, noting how the brittle 



