72 



THE FOOD OF ANIMALS 



those most addicted to animal food are to be found, and decidedly 

 the most aggressive of these are the American Snapper- Tortoises, 

 of which an example is the Alligator- Terrapin [Chelydra serpentina), 

 which ranges from Canada to Ecuador on the eastern side of the 

 mountain axis of the New World. As the common name suggests, 

 there is a powerful flattened tail, which serves as an efficient swim- 



Fig. 360. — Hawk-bill Turtle {Clielone imhricata) 



ming organ, enabling the animal to overtake the frogs and fish 

 upon which it chiefly feeds. Its powerful jaws are covered with a 

 strong horny sheath, and they are brought together with a sudden 

 and effective snap at the psychological moment. The Hawk-bill 

 Turtle {Chelone imbricata), from which the "tortoise-shell" of com- 

 merce is obtained, is also purely carnivorous in habit, and its 

 hooked beak is correlated with the nature of its food (fig. 360). 



In most Chelonians the rigidity of the trunk is made up for 

 by the extreme mobility of the neck, and in some members of the 

 order this would appear to be of importance in the capture of prey. 

 The Snake-necked Tortoises i^Hydromedusa) of South America, 

 for example, possess exceedingly long necks, which can either be 

 folded back within the shell or thrust out with great swiftness. 



