REPTILIA 261 



GENERAL REMARKS ON THE ORDER SQUAMATA 



Lizards are clearly more generalized animals than snakes. 

 Most of them possess four well-developed legs with toes, 

 though there are a few which agree with snakes in lacking 

 any external indication of appendages in the adult condi- 

 tion. Snakes are specialized in the absence of appendages, 

 the structure of their jaws, and in other particulars. Yet, 

 despite the divergences between snakes (Serpentes) and 

 lizards (Sauria) , their fundamental plans of structure are 

 so similar that they are placed by systematic zoologists in 

 one order. , 



It cannot be said, however, that many lizards are not 

 specialized; some, indeed, are highly adapted to peculiar 

 modes of life. The limbless species all burrow, and are 

 seldom seen above the surface of the ground. The flying- 

 dragon, Draco volans, has thin lateral expansions on the 

 body which are supported by the ribs and furnish enough 

 Surface so that the animal can sail from tree to tree. The 

 chameleons have prehensile feet and tail, hence are able to 

 climb with great sureness, and their remarkably extensible 

 tongue enables them to snap up insects among the trees. 

 Their unusual ability to change the colors of their skins 

 is also noteworthy. The ," horned toads" are adapted to 

 life in the desert. They are spiny, burrow to escape ex- 

 treme heat or cold, and have other adaptations which 

 enable them to live in arid localities. 



The largest lizards in America are the iguanas, which 

 range from the southern United States southward. They 

 attain a length of six feet, and are often eaten by man. 

 They eat vegetation, insects, bird's eggs, and animals up 

 to the size of a half-grown rabbit. Through the southern 

 states the little aaoles are very common among plants. 

 They are easily tamed and are often sold by curio dealers. 

 The only poisonous lizards known live in the southern 

 United States and Mexico. These Gila monsters (Helo- 

 derma) are sluggish but powerful creatures with bands of 



