REPT1LIA 213 



hind limbs only, and two or three species in which fore 

 limbs only are present. The study of fossil reptiles shows 

 that the ancestors of these forms had well-developed limbs 

 which degenerated on account of the habits of the animals ; 

 they spend much time in narrow quarters where legs are 

 useless and a hindrance. 



The only poisonous lizard in this country is the Gila 

 monster (Heloderma suspedum) living in Arizona, Cali- 



FIG. 244. The Gila monster. Photograph one fifth natural size. 



fornia, and Mexico. The largest specimens measure nearly 

 a yard. Allied to these are the huge monitor lizards of 

 Africa, India, and Australia, which attain a length of seven 

 feet. Most lizards are oviparous, depositing their eggs 

 in the sand. 



The Ophidia. The snakes, numbering one hundred and 

 fifty species in North America, are much more elongated 



