UNOULATA. 371 



to the female of the same genus. Bramatherium and Vishnu- 

 therium are more imperfectly known contemporaneous genera 

 from the Indian region. 



The existing prong-buck (Antilocaprd) of the North 

 American prairies is well known to be partly intermediate 

 between the Cervidae and the Bovidae in the nature of its 

 horns ; and the hinder appendages of Sivatherium, as also the 

 horns of several other early ruminants, may well have been 

 similar to these structures. The horns have a permanent bony 

 core, as in the Bovidae; but the epidermal sheath does not 



FIG. 210. 



Sivatherium giganteum ; partially restored skull, anterior aspect, one-thirteenth 

 nat. size. L. Pliocene (Siwalik Formation) ; India. (After Lydekker.) 



merely wear away, it is periodically shed like the antlers of the 

 Cervidse. The gap between the solid-horned (cervicorn) and 

 hollow-horned (cavicorn) ruminants, is thus partly filled even 

 in the existing world. 



In the true Bovidae, or antelopes, sheep, and oxen, the 

 frontal appendages when present are always a pair of persistent 

 bony processes (horn-cores), covered with true horn, which 

 grows continuously at the base and is worn away at the apex. 

 These are the most specialized of all the artiodactyls, and 



242 



