296 THE VERTEBRATE ANIMALS 



Poisonous Snakes. Not all snakes can be said to be harmless. The 

 bite of the rattlesnake of our own country, although dangerous, seldom 

 kills. The dreaded cobra of India has a record of over two hundred and 

 fifty thousand persons killed in the last thirty-five years. The Indian 

 government yearly pays out large sums for the extermination of venomous 

 snakes, over two hundred thousand of which have been killed during a 

 single year. 



Alligators and Crocodiles. The latter are mostly confined to Asia 

 and Africa, while the former are natives of North and South America. 

 The chief structural difference between them is that the teeth in alligators 



Young alligator. One fourth natural size. 



are set in long sockets, while those of the crocodile are not. Both of 

 these great lizardlike animals have broad, vertically flattened tails adapted 

 to swimming. The eyes and tip of the snout, the latter holding the nos- 

 tril holes, protrude from the head, so that the animal may float motion- 

 less near the surface of the water with only eyes and nostrils visib'e. The 

 nostrils are closed by a valve when the animal is under water. These rep- 

 tiles feed on fishes, but often attack large animals, as horses, cows, and 

 even man. They seek their prey chiefly at night, and spend the day bask- 

 ing in the sun. The crocodiles of the Ganges River in India levy a yearly 

 tribute of many hundred lives from the natives. 



Characteristics of Reptilia. The animals described belong 

 to the class of vertebrates known as Reptilia. Such animals 

 are characterized by having scales developed from the skin. These 

 in the turtle have become bony and are connected with the internal 

 skeleton. Reptiles always breathe by means of lungs, differing in 

 this respect from the amphibians. They show their distant 



