422 GENERAL ZOOLOGY 



ca'nus). The latter can be distinguished from the former 

 by its very large ears. The Asiatic species has long been 

 domesticated and many stories are told of its intelligence. 

 The African species was used by the Romans in battle and 

 circus games, but in modern times these animals have been 

 hunted so persistently for their ivory that there is danger of 

 their being exterminated. Steps are now being taken to pre- 

 vent their complete destruction. 



Gnawing Mammals. The Roden'tia (Lat. rodere, " gnaw ") 

 are the most numerous in point of species and are the most 

 widely distributed of all the mammals. Here belong the 

 hares, rabbits, guinea pigs, porcupines, mice, rats, beavers, 

 woodchucks, prairie dogs, and squirrels. Rodents are dis- 

 tinguished by the absence of canine teeth and the presence 

 of chisel-shaped incisors, which grow from persistent pulps 

 (Fig. 214). They are mostly terrestrial animals, though a 

 few, like the beaver, are modified for an aquatic existence, 

 and others, like the squirrels, for life in the trees. 



The hares are distinguished from all other rodents by the 

 presence of a second pair of incisor teeth behind the first pair 

 in the upper jaw. Well-known American species are the cot- 

 tontail, or gray rabbit, of the East (Sylvila'gus florida'nus), 

 the varying hare (Le'pus america'nus) of the North, and the 

 northern jack rabbit (Lepus campes'tris) of the West. The 

 cottontail is so named from the white tail, which is plainly 

 shown in flight and probably serves as a signal or recogni- 

 tion mark. The varying hare is a larger and more northern 

 species, which grows a white coat of fur in winter. The north- 

 ern jack rabbit also changes to white in the northern part of 

 its range ; farther south the change is only partial or entirely 

 wanting. The domestic rabbit is descended from the com- 

 mon rabbit of the Mediterranean basin (Lepus cunic'ulus). 



The porcupine (Erethi'zon dorsa'tus) is a sluggish, stupid 

 animal, which, having spines for protection, relies on them 



