610 The Animal Kingdom 



parently they detect the location of warm-blooded prey and may be 

 useful in directing the strike. 



In the New World tropics, most of the snakes are of the non- 

 poisonous type; however, there are a few dangerous ones. The bush- 

 master, Lachesis muta, the fer-de-lance, Bothrops atrox, and the tropi- 

 cal rattlesnakes are all examples of the pit vipers. The most spec- 

 tacular of the tropical snakes are the large nonpoisonous boa constrictors, 

 Constrictor constrictor, which may be as long as 10 or 15 feet. The 

 largest of these are the anacondas, Eimectes murinus, which attain 

 lengths of 25 feet and live in the forests of the Amazon basin. In 

 the Old World tropics, the python is the largest form, attaining lengths 

 up to 30 feet. Of interest is the fact that the python has vestigial 

 hind appendages. 



Some of the most dangerous poisonous snakes of the Old World are 

 relatives of our coral snakes. The cobras of the genus Naja and the 

 kraits of the genus Bungarus are the most famous forms. 



Although most snakes are terrestrial in habit, a few have become 

 thoroughly adjusted to sea life. These are the sea snakes of the sub- 

 family Hydrophinae. These have flattened tails for swimming and 

 come to land only briefly. Their venom is very effective against fish, 

 which constitute their chief food. 



Snake Legends. — Probably no group of animals has as many false 

 stories told about it as do the snakes. Incorrect ideas include such 

 stories as snakes swallowing their young, the fact that they do not 

 die until sundown, their ability to form a hoop and roll rapidly toward 

 unsuspecting prey, and that snakes will not cross horsehair ropes. No 

 doubt a little reflection on anyone's part would add many more stories 

 to this very brief list of inaccuracies. 



The Order Crocodilia. — The largest of the living reptiles are 

 the crocodiles, alligators, caimans, and gavials. These giant, lizardlike 

 reptiles are found throughout the tropical and subtropical regions of 

 the world. 



Essentially these animals are aquatic forms which are very awk- 

 ward and slow moving on land. Their heavy bodies are dragged over 

 the ground by the short legs, but in water, these same awkward creatures 

 are fast moving and agile. The flattened tail is the chief locomotor organ. 

 Although the general form of the alligators and crocodiles is quite simi- 

 lar to that of the lizards, the nose is much elongated and the nostrils 

 are at the tip. The eyes are well back from the tip of the nose and are 



