PORCUPINES. 



85 



almost invariably one premolar above and below, a peculiarly twisted 

 lower jaw, variable palatine foramina, generally no postorbital pro- 

 Fig. 43. 



Lower hind leg of Rat. 

 f. fibula ; t, tibia. 



cesses, and separate sbin-bones. The animals forming tbis section 

 are very variable botb in size and osteological characters. The 

 most noteworthy are the true Porcupines (Hystrix), which have 



Fij?. 44. 



Skull of Common Porcupine (Hystrix cristatd). The outer part of the 

 bone of the lower jaw has been removed, to show the whole length of 

 the lower incisor tooth. 



i, incisor teeth ; m, molars ; pm, premolars. 



the facial part of the skull curiously dilated (see fig. 44) ; the 

 Capybara (Hydrochoerus capybara}, the largest of the Rodents; 



