390 SYSTEMATIC ZOOLOGY 



West is eaten by the Indians, and has the reputation of being 

 a great thief, carrying off all sorts of useless objects. Some 

 interesting members of this group are confined to Europe, Asia, 

 and Africa ; among these are the hamsters, which have highly 

 developed cheek pouches, and the minute dormice, only about 

 seven centimeters long, with a tail like a squirrel's ; both of 

 these hibernate during the winter. 



Suborder 3. Hystricomorpha 



The Hystricomorpha (Gr. varpig, porcupine, and /jLop<t>Ti, 

 form), or porcupine-like rodents, comprise animals which differ 

 very widely in external appearance. The majority inhabit the 

 western hemisphere, and South America contains the largest 

 number. To this group belongs the largest living rodent, the 

 water cavy or capybara, which inhabits South America, espe- 

 cially Brazil ; it is sometimes called the water pig because of its 

 general shape and the fact that it takes so readily to the water. 

 The body is about a meter and a quarter long, half a meter 

 high, and is covered with coarse hair ; the tail is very rudi- 

 mentary. Perhaps next in size is the Patagonian cavy, from 

 seventy-five to ninety centimeters long and thirty high. The 

 little guinea pigs, of which there are several species, are con- 

 fined to South America. One of the most common, Cavia coboya, 

 is often domesticated, and is extremely prolific. It is born with 

 its permanent teeth, the milk dentition disappearing during fetal 

 life. Economically the most valuable members of this group 

 are the chinchillas, varying in length from twenty-five to thirty- 

 five centimeters, with a tail about half as long ; their soft silver- 

 gray fur is familiar to every one ; thev live in Peru, Bolivia, and 

 Chi'le. 



Very different from these in general appearance are the 

 porcupines, which have some of the hairs modified into stiff 

 spines or " quills," barbed at the end in many species. The 

 American species are more or less arboreal in habit, with thick 

 fur and relatively short quills ; those inhabiting North America 

 are the larger and average about three quarters of a meter in 

 length. The tail is the principal weapon of defense and is 

 manipulated with great speed and skill. That porcupines can 



