THE VERTEBRATES 427 



of many reptiles, and some can quickly change color (e.g., 

 chameleons). 



Most reptiles are tenacious of life and many can exist for 

 a long time without food and with limited breathing. A 

 winter sleep in cold climates, and a summer, or dry-season 

 sleep in hot climates, is their rule of life. 



Fossil reptiles have attracted much attention because of 

 their gigantic size, some of them being over 100 feet long. 

 Dinosaurs (bird-like reptiles), Pterosaurs (flying reptiles), 

 Ichthyosaurs (fish-like reptiles), and Plesiosaurs (lizard-like), 

 are some of the fossil reptiles commonly seen in great mu- 

 seums. So abundant were these and other reptiles that one 

 stage of geological history has been called the Age of Reptiles. 

 In North America the best specimens of fossil reptiles are 

 found in Wyoming and adjoining states. 



353. Economic Relations of Reptiles. Most lizards are 

 harmless, and may be useful as destroyers of insects. Igua- 

 nas and other large species are hunted for their flesh. 

 The Gila monster of Arizona may sometimes inflict a poison- 

 ous bite. Brilliantly colored lizards are often kept as pets ; 

 they should be fed insects, and not starved on sugar and 

 water. (Why?) 



Many turtles are valuable as human food. Terrapin 

 turtles are now so very high in price that " terrapin-farms " 

 are profitable. 



Snakes feed exclusively on living animals, and hence may 

 be more or less harmful from our human viewpoint, espe- 

 cially those which destroy insectivorous birds and frogs. 

 Poisonous snakes belong to many different families. The 

 American moccasins, rattlesnakes, and copperheads, and 

 the Old World cobra, adders, and vipers are the most poison- 

 ous reptiles. Official figures show that in India alone more 

 than 20,000 people die annually from snake bites, but there 

 are few fatal cases in the United States. Pythons, boas, 

 and American blacksnakes are examples of snakes which 



