194 FIELD MUSEUM OF NATURAL HISTORY ZOOLOGY, VOL. X. 



ish at the base, the ears are thinly haired and dusky, and in the skull the 

 jugal has a well-developed postorbital process. In all of these respects 

 D. nigriclunis is markedly different, the sides of the rump being mixed 

 tawny and black, the long rump hairs are dark drab at the base, the 

 ears are hairy and light ferruginous in color, and in the skull the jugal 

 shows scarcely an indication of a postorbital process. The type of 

 D. nigriclunis is slightly immature, for although the last molar is up in 

 place and somewhat worn, the milk tooth is still in the last stages of 

 functional condition. It is possible that an older individual might show 

 some development of a postorbital process of the jugal, but this is 

 rendered improbable by the fact that in various of the yellow-rumped 

 species it is well marked in specimens younger than the type of nigri- 

 clunis. 



Caviella subg. nov. 



Type, Cavia australis Geoffrey & D'Orbigny. 



Characters: Intermediate, in a broad sense, between Cavia and 

 Galea, having certain general cranial characters of Cavia and dental 

 characters of Galea; palatine foramina large and roughly triangular, 

 their length at least half the diastema; orbital branch of maxillary con- 

 tinuous as in Cavia, not broadly interrupted by lacrymal as in Galea; 

 palate with a central ridge and deep lateral channels; rostral and inter- 

 orbital region nearly flat, not laterally sloping; lateral boundary of 

 rostrum formed almost entirely by thepremaxillae, the shelflike develop- 

 ment of the maxillaries found in Cavia and Galea being so reduced that 

 the lower border of the infraorbital foramen is clearly visible when the 

 skull is viewed from directly above; incisors projected well beyond the 

 nasals, unpigmented as in Cavia; cheekteeth closely similar to those of 

 Galea, the enamel loops of the middle teeth nearly equal in size and the 

 posterior loop with no angle on its outer side. 



Remarks: Examination of a considerable series of skins, skulls, 

 and skeletons of various species usually referred to Cavia and Kerodon 

 indicates that a natural arrangement of generic and subgeneric groups 

 requires some changes in the application of names. The name Kerodon 

 should be restricted to one species, Kerodon rupestris, which not only 

 differs from the others in habits, in external characters, and in cranial 

 characters, but in important skeletal characters. Chief of these are the 

 narrow and rounded instead of flattened sternum, the thick, heavy, and 

 depressed spinous processes of the lumbar vertebrae, the large neural 

 spine of the axis fully overlapping the first cervical, and the transverse 

 processes of the atlas which are singly instead of doubly perforated on 



