The terrestrial animals of the Pliocene period present us with a great number of creatures alike remarkable from their proportions and from their structure. The Mammals and the batrachian Reptiles are alike deserving of our attention in this epoch. Among the former the Mastodon, which makes its first appearance in the Miocene formations, continues to be found, but becomes extinct apparently before we reach the upper beds. Others present themselves of genera totally unknown till now, some of them, such as the _Hippopotamus_, the _Camel_, the _Horse_, the _Ox_, and the _Deer_, surviving to the present day. The fossil horse, of all animals, is perhaps that which presents the greatest resemblance to existing individuals; but it was small, not exceeding the ass in size. [Illustration: Fig. 175.--Head of Rhinoceros tichorhinus, partly restored under the direction of Eugene Deslongchamps.] The _Mastodon_, which we have considered in our description of the preceding period, still existed in Pliocene times; in Fig. 174 the species living in this latter age is represented--it is called the Mastodon of Turin. As we see, it has only two projecting tusks or defences in the upper jaw, instead of four, like the American species, which is described in page 343. Other species belonging to this period are not uncommon; the portion of an upper jaw-bone with a tooth which was found in the Norwich Crag at Postwick, near Norwich, Dr. Falconer has shown to be a Pliocene species, first observed in Auvergne, and named by Messrs. Croizet and Jobert, its discoverers, _Mastodon Arvernensis_. The _Hippopotamus_, _Tapir_, and _Camel_, which appear during the Pliocene period, present no peculiar characteristics to arrest our attention. The Apes begin to abound in species; the Stags were already numerous. The _Rhinoceros_, which made its appearance in the Miocene period, appears in greater numbers in the Pliocene deposits. The species peculiar to the Tertiary epoch is _R. tichorhinus_, which is descriptive of the bony partition which separated its two nostrils, an anatomical arrangement which is not found in our existing species. Two horns surmount the nose of this animal, as represented in Fig. 175. Two living species, namely, the Rhinoceros of Africa and Sumatra, have two horns, but they are much smaller than those of _R. tichorhinus_. The existing Indian Rhinoceros has only one horn. The body of _R. tichorhinus_ was covered with very thick hair, and its skin was without the rough and callous scales which we remark on the skin of the living African species.