CHORDATA 



317 



has been killed the other will otter, appear and remain beside 

 its dead companion for a long time. To man}- people they 

 the most repulsive of animals, and many species are certainly 

 the most venomous. 



A convenient popular classification of the serpents, which is 

 also justified to some extent scientifically, is into the non-poison- 

 ous and the poisonous. We may note a few oi each kind. 

 Among the non-poisonous snakes are a few small species, from 

 a few centimeters to half a meter in length, which live under- 

 ground and resemble to a considerable extent the legless lizards. 

 Like them the jaws are not distensible and the eyes are small. 

 On the other hand, some of the largest tropical serpents are not 

 poisonous, but rely on their great strength to kill their prey by 

 crushing it. Among these are the pythons, or rock snakes, 

 which belong to the eastern hemisphere, particularly to the 

 tropical regions of Africa, Asia, and Australia. The stories of 

 these serpents are more wonderful than the animals themselves. 

 In size, the largest actually measured is said to have been a little 

 over six meters long, and from three to four meters is considered 

 tod-sized python. Their food consists chiefly of birds and 

 small quadrupeds, which they capture when they come to the pools 

 to drink, where the python lies in wait. The largest animal 

 which they can swallow is about the size of a small dog. These 

 serpents possess rudimentary hind legs. After laying her e{ 

 the female python coils herself over them and thus protects 

 them during incubation. The royal rock snake of western 

 Africa, Python regia, is frequently seen in menageries. 



Corresponding in size to the pythons are the boas, which are 

 distinctly American serpents. The emperor snake, Boa impera- 

 tor, of Central America and Mexico is brownish in color and 

 closely resembles the more familiar Boa constrictor of Brazil. 

 Related to the boas is the anaconda, also a tropical American 

 snake. Of the smaller non-poisonous snakes many have a bad 

 reputation because of their repulsive appearance. The puffing 

 adder or sand viper, Heterodon platyrhinos, a large and ugly- 

 looking snake found east of the Mississippi, is perfectly harm- 

 less. The common black snake, which attains a length of a 

 meter or more, is found all over the United States from the 

 Atlantic to the Pacific ; it often lives near the water and coiled 



