RODENTIA. 307 



peculiarities give origin. There are two species, one 

 of North America, the other of Europe, more chiefly 

 confined to Poland, under the name of Bobr. FIBER 

 or ONDATRA, a second genus, shaped like an enor- 

 mous rat, with a long and compressed tail, of which 

 the F. zibethicus, or Musk Rat of North America, 

 is the only species. Then the genus ARVICOLA 

 Proper, which includes our Water Rat, Field 

 Mouse, &c., forming twenty-eight species. The 

 genus LEMMUS, the Lemmings, with four or five 

 toes on the anterior feet, eight species ; SPALAX, or 

 Blind Rats, two ; and GEOMYS, ten species. 



HYSTRICINA. In the second division are placed 

 the Rodents with imperfect clavicles, of which the 

 first family is that of Hystridoe, or Porcupines, form- 

 ing the sub-genera HYSTRIX, ERETHISON, CERCO- 

 LABES, ATHERURUS, and SYNETHERES, to include 

 only ten species, of which the Crested Porcupine, 

 H. cristata, is the most conspicuous; Erethison Buf- 

 fonii, or Prehensile Tailed Porcupine, the most com- 

 mon in museums. The Canada Porcupine, E. 

 dorsata> we have seen defending itself by striking 

 with the cluster of spines at the end of its tail, 

 leaving some of them sticking in the hand of the per- 

 son who gave it offence. 



The next group contains the Dasyproctidce, the 

 Agoutis. The cheek teeth |-|, four toes and tuber- 

 cles on the fore feet, three toes on the hinder, sole 

 of the feet callous, naked. They inhabit South 

 America and the West India Islands : three or four 

 species. We have seen D. Acmcliy, or Olive Agouti, 



