CHAPTER XXXIII 

 R ODEN TS continued 



THE PORCUPINE-LIKE RODENTS 

 Families OCTODONTID^E, HTSTRICID^, etc. 



THE Rodents described in the present chapter, which include the whole of the 

 remaining members of the order, with the exception of the hares, rabbits, and picas, 

 are distinguished from all those described above by the conformation of the lower 

 jaw. In both the squirrel-like and mouse-like groups, the angular, or lower poste- 

 rior process of the lower jaw, it will be remembered, takes its origin from the 

 inferior edge of the socket of the lower incisor teeth. In the present group, on the 



SKELETON OF THE CANE RAT. 



other hand, this process originates from a prominent ridge on the outer side of the 

 jaw; the position of this ridge being shown in the figure of the skeleton of the cane 

 rat. All the members of the group are further characterized by the stoutness of the 

 zygomatic or cheek arch of the skull, and also by the bones of the lower leg (tibia 

 and fibula) being perfectly distinct from one another. 



The porcupine-like Rodents are very characteristic of America, and more 

 especially of the southern half of the continent. Thus the whole six families into 

 which the group is divided occur in America, while only two of them have any Old- 

 World representatives. Of the latter, the Porcupine family is almost cosmopolitan; 

 while the Octodontida: are represented in the Old World only in Africa, south of the 

 Sahara. With the exception of one species, these Rodents have one pair of pre- 

 molar teeth in each jaw. 

 (1326) 



