tween the typical
Antelopes and the Goats. Perhaps the most remarkable, however,
of these Miocene Ruminants is the _Sivatherium giganteum_ (fig.
245) of the Siwalik Hills, in India. In this extraordinary animal
there were two pairs of horns, supported by bony "horn-cores,"
so that there can be no hesitation in referring _Sivatherium_
to the Cavicorn Ruminants. If all these horns had been simple,
there would have been no difficulty in considering _Sivatherium_
as simply a gigantic four-horned Antelope, essentially similar
to the living _Antilope_ (_Tetraceros_) _quadricornis_ of India.
The hinder pair of horns, however, is not only much larger than
the front pair, but each possesses two branches or snags--a
peculiarity not to be paralleled amongst any existing Antelope,
save the abnormal Prongbuck (_Antilocapra_) of North America.
Dr Murie, however, in an admirable memoir on the structure and
relationships of _Sivatherium_, has drawn attention to the fact
that the Prongbuck sheds the _sheath_ of its horns annually,
and has suggested 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.

[Illustration: Fig. 245.--Skull of _Sivatherium giganteum_, reduced
in size. Miocene, India. (After Murie.)]

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 (_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 _Deinotherium_, the
equally extinct _Mastodons_, and the _Elephants_; and all these
three types are known to have been in existence as early as the
Miocene period, the first of them being exclusively confined to
deposits of this age. Of the three, the genus _Deinotherium_
is much the most abnormal in its characters; so much so, that
good authorities regard it as really bei