en-toed or _Artiodactyle_ Ungulates, we for the
first time meet with examples of the _Hippopotamus_, with its
four-toed feet, its massive body, and huge tusk-like lower canine
teeth. The Miocene deposits of Europe have not hitherto yielded
any remains of _Hippopotamus_; but several species have been
detected in the Upper Miocene of the Siwalik Hills by Dr Falconer
and Sir Proby Cautley. These ancient Indian forms, however, differ
from the existing _Hippopotamus amphibius_ of Africa in the fact
that they possessed six incisor teeth in each jaw (fig. 244),
whereas the latter has only four.

[Illustration: Fig. 244.--a, Skull of _Hippopotamus Sivalensis_,
viewed from below, one-eighth of the natural size; b, Molar
tooth of the same, showing the surface of the crown, one-half
of the natural size: c, Front of the lower jaw of the same,
showing the six incisors and the tusk-like canines, one-eighth of
the natural size. Upper Miocene, Siwalik Hills; (After Falconer
and Cautley.)]

Amongst the other Even-toed Ungulates, the family of the Pigs
(_Suida_) is represented by true Swine (_Sus Erymanthius_), Peccaries
(_Dicotyles antiquus_), and by forms which, like the great
_Elotherium_ of the American Miocene, have no representative at
the present day. The Upper Miocene of India has yielded examples
of the Camels. Small Musk-deer (_Amphitragulus_ and _Dremotherium_)
are known to have existed in France and Greece; and the true Deer
(_Cervidoe_), with their solid bony antlers, appear for the first
time here in the person of species allied to the living Stags
(_Cervus_), accompanied by the extinct genus _Dorcatherium_. The
Giraffes (_Camelopardalidoe_), now confined to Africa, are known to
have lived in India and Greece; and the allied _Helladotherium_, in
some respects intermediate between the Giraffes and the Antelopes,
ranged over Southern Europe from Attica to France. The great
group of the "Hollow-horned" Ruminants (_Cavicornia_), lastly,
came into existence in the Miocene period; and though the typical
families of the Sheep and Oxen are apparently wanting, there are
true Antelopes, together with forms which, if systematically
referable to the _Antilopidoe_, nevertheless are more or less
clearly transitional between this and the family of the Sheep and
Goats. Thus the _Paloeoreas_ of the Upper Miocene of Greece may
be regarded as a genuine Antelope; but the _Tragoceras_ of the
same deposit is intermediate in its characters be