290 



ZOOLOGY 



for protection, their noiseless movement, protective color, and, in 

 some cases, by their odor and poison. 



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 thou- 

 sand 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 this continent and 



Young alligator. One fourth natural size. 



South America. The chief structural difference between them is 

 that the teeth in alligators are set in long sockets, while those of 

 the crocodile are not. Both of these great lizardlike animals have 

 broad, flattened tails adapted to swimmmg. The eyes and nostril 

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

 less near the surface of the water with only eyes and nostrils 

 visible. The nostrils are closed by a valve when the animal is 

 under water. They feed on fishes, but are known to attack large 

 animals, as horses, cows, and even man. They seek their prey 

 chiefly at night ; and spend the day basking in the sun. The croc- 

 odiles of the Ganges River in India levy a yearly tribute of many 

 hundred lives from the natives. 



