RODENTIA : HYSTRICIDyE. 77 



general color is dark brown above, rusty brown below. 

 Muskrats feed upon mussels and roots of grasses and 

 aquatic plants, and build winter houses of mud, sticks, 

 and grass, and having an entrance under the water which 

 leads to a dry apartment above. In summer they dig 

 burrows of great extent along the banks, in which they 

 bring forth their young. They are good swimmers, mov- 

 ing with ease and considerable rapidity. At early even- 

 ing, or on a moonlight night, they may be seen swim- 

 ming from bank to bank, or log to log, and often sporting 

 together in the most playful manner. 



4. Spalacinae, comprising the Blind Rat-Moles of the 

 Old World, may perhaps be considered a fourth sub- 

 family of Muridae. 



HYSTRICID^:, OR PORCUPINE FAMILY. This Family 

 comprises a large number of Rodents, which at first view 

 seem very different from one another, but which are 

 united by important characters. The molars are - , and 

 the terminal portion of the muzzle is clothed with small 

 hairs. They are mainly American, and chiefly confined 

 to the southern portion of the continent. 



The Genus Erethizon Porcupines is characterized 

 by a flat cranium, short muzzle, medium-sized tail, and 

 spines which are short and half hidden in the hair. 



The White-haired or Canada Porcupine, E. dorsatus, 

 F. Cuv., of Northern United States and Canada, is about 

 two feet long to the tail, which is seven inches. The 

 tail and upper parts are covered with a mass of white 

 spines with dusky and bearded tips. The general color 

 of the fur is dark brown, among which are long hairs 

 with white tips. This animal is extremely sluggish, mak- 

 ing but little effort to escape from man or beast ; but 

 its formidable armor is an effectual defence. It readily 

 climbs trees, and feeds upon bark, leaves, and tender ears 

 of Indian corn. It lives in hollow trees and in holes 

 among the rocks. 



