THE MIOCENE PERIOD. 319 



of Sivatherium, has drawn attention to the fact that the Prong- 

 buck sheds the sheath of its horns annually, and has suggested 



Fig. 245. Skull of Sivatherittm gigantett m, reduced in size. Miocene, India. 

 (After Murie.) 



that this may also have been the case with the extinct form. 

 This conjecture is rendered probable, amongst other reasons, 

 by the fact that no traces of a horny sheath surrounding the 

 horn-cores of the Indian fossil have been as yet detected. 

 Upon the whole, therefore, we may regard the elephantine 

 Sivatherium as being most nearly allied to the Prongbuck of 

 Western America, and thus as belonging to the family of the 

 Antelopes. 



It is to the Miocene period, again, to which we must refer 

 the first appearance of the important order of the tlephants 

 and their allies (Proboscideans}, all of which are characterised by 

 their elongated trunk-like noses, the possession of five toes to 

 the foot, the absence of canine teeth, the development of two 

 or more of the incisor teeth into long tusks, and the adaptation 

 of the molar teeth to a vegetable diet. Only three generic 

 groups of this order are known namely, the extinct Deino- 

 therium, the equally extinct Mastodons, and the Elephants ; and 

 all these three types are known to have been in existence as 



