THE REPTILIA 331 



average length of four feet. This species, the copperhead, and 

 rattlesnakes are all known as pit vipers because of the presence 

 of a deep pit between each eye and the nostril. These pits are 

 so small, however, that a snake must be examined rather closely in 

 order to determine w r hether or not they are present. Hence one 

 must rely on other characteristics to identify them at a distance. 



The copperhead (Fig. 209) is another poisonous snake of the 

 southeastern United States. It occurs on the plantations and in 

 or near forests, and is about two and one half feet long. 



The harlequin snake and coral snake are so small as to be of 

 very little importance, but their relative, the cobra-de-capello 

 of the Orient, is a very dangerous reptile. In a single year (1908) 

 about twenty-thousand natives were killed by cobras in India. 



CROCODILES AND ALLIGATORS 



Crocodiles and their near relatives look very much like large 

 lizards (Fig. 210). They are adapted for life in the water, with 

 the toes of the hind feet more or less webbed, and the tail com- 

 pressed laterally, making it an effective swimming organ. The 

 exoskeleton of the crocodile consists of a thick, leathery skin, 

 covered with horny scales and horny plates, and is, therefore, a 

 good protection from injury. Several of the internal organs of 

 these reptiles are worth mentioning here. The ventricle of the 

 heart is completely divided into two parts by a partition (see p. 

 311), and the body cavity is divided into two chambers as in 

 mammals, the anterior chamber containing the lungs. 



The American crocodile occurs along the streams from Florida 

 southward into South America. Its head is broad at the base 

 and narrow at the snout, whereas that of the alligator is wider 

 at the snout. The crocodile reaches a length of fourteen feet. 

 When in the w r ater it floats at the surface with just its eyes and 

 the nostrils at the end of the snout protruding. It can thus 

 both see and breathe without itself being seen. The crocodile 

 of Africa is a very dangerous man eater and kills hundreds of 

 natives every year. 



