THE MIOCENE PERIOD. 319 
' 
of Szvatherium, has drawn attention to the fact that the Prong- 
buck sheds the sheath of its horns annually, and has suggested 
Fig. 245.—Skull of Stvatherium giganteum, 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 
Stvatherium 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 Elephants 
and their allies (fv oboscideans), 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 Deno- 
therium, the equally extinct AZastodons, and the Elephants ; and 
all these three types are known to have been in existence as 
