THE MIOCENE PERIOD. aa7. 
as has been previously mentioned, differed from that of the 
Horse in the fact that whilst both possess the middle toe greatly 
developed and enclosed in a broad hoof, the former, in addition, 
possessed two lateral toes, which were sufficiently developed 
to carry hoofs, but were so far rudimentary that they hung idly 
by the side of the central toe without touching the ground 
(see fig. 230). In the Horse, on the other hand, these lateral 
toes, though present, are not only functionally useless, but are 
concealed beneath the skin. Remains of the Azpparion have 
been found in various regions in Europe and in India; and _ 
from the immense quantities of their bones found in certain 
localities, it may be safely inferred that these Middle Tertiary 
ancestors of the Horses lived, like their modern representa- 
tives, in great herds, and in open grassy plains or prairies. 
Amongst the Even-toed or Artiodactvle Ungulates, we for 
the first time meet with examples of the Wzppopotamus, 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 A7ppopotamus ; 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 [/7ppopotamus 
amphibius of Africa in the fact that they possessed six incisor 
teeth in each jaw (fig. 244), whereas the latter has only four. 
Amongst the other Even-toed Ungulates, the family of the 
Pigs (Swzd¢a) is represented by true Swine (Sus Erymanthius), 
Peccaries (Dicotyles antiguus), and by forms which, like the 
great L/otherium of the American Miocene, have no represen- 
tative at the present day. The Upper Miocene of India has 
yielded examples of the Camels. Small Musk-deer (AmpAz- 
tragulus and Dremotherium) are known to have existed in 
France and Greece; and the true Deer (Cervide), with their 
solid bony antlers, appear for the first time here in the person of 
species allied to the living Stags (Cerzus), accompanied by the 
extinct genus Dorcatherium. The Giraffes (Camelopardalide), 
now confined to Africa, are known to have lived in India and 
Greece; and the allied Wel/adotherium, in some repects inter- 
mediate 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 systemati- 
cally referable to the Andzlopide, nevertheless are more or less 
clearly transitional between this and the family of the Sheep 
