Amongst the Even-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 Siwâlik 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.
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 (Cervidœ), 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 (Camelopardalidœ), 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 Antilopidœ, nevertheless are more or less clearly transitional between this and the family of the Sheep and Goats. Thus the Palœoreas of the Upper Miocene of Greece may be regarded as a genuine Antelope; but the Tragoceras of the same deposit is intermediate in
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, Siwâlik Hills; (After Falconer and Cautley.) its characters between the typical Antelopes and the Goats. Perhaps the most remarkable, however, of these Miocene Ruminants is the Sivatherium giganteum (fig. 245) of the Siwâlik 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
Fig. 245.—Skull of Sivatherium giganteum, reduced in size. Miocene, India. (After Murie.) 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.
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 being one of the Sea-cows (Sirenia)—though this view has been rendered untenable by the discovery of limb-bones which can hardly belong to any other animal, and which are distinctly Proboscidean in type. The most celebrated skull of the Deinothere (fig. 246) is one
Fig. 246.—Skull of Deinotherium giganteum, greatly reduced. From the Upper Micene of Germany. which was exhumed from the Upper Miocene deposits of Epplesheim, in Hesse-Darmstadt, in the year 1836. This skull was four and a half feet in length, and indicated an animal larger than any existing species of Elephant. The upper jaw is destitute of incisor or canine teeth, but is furnished on each side with five molars, which are opposed to a corresponding series of grinding teeth in the lower jaw. No canines are present in the lower jaw; but the front portion of the jaw is abruptly bent downwards, and carries two huge tusk-like incisor teeth, which are curved downwards and backwards, and the use of which is rather problematical. Not only does the Deinothere occur in Europe, but remains belonging to this genus have also been detected in the Siwâlik Hills, in India.
The true Elephants (Elephas) do not appear to have existed during the Miocene period in Europe, but several species have been detected in the Upper Miocene deposits of the Siwâlik Hills, in India. The fossil forms, though in all cases specifically, and in some cases even sub-generically, distinct, agree with those now in existence in the general conformation of their skeleton, and in the principal characters of their dentition. In all, the canine teeth are wanting in both jaws; and there are no incisor teeth in the lower jaw, whilst there are two incisors in the front of the upper jaw, which are developed into two huge "tusks." There are six molar teeth on each side of both the upper and lower jaw, but only one, or at most a part of two, is in actual use at any given time; and as this becomes worn away, it is pushed forward and replaced by its successor behind it. The molars are of very large size, and are each composed of a number of transverse