_Cetacea._--Species of _Balæna_, _Physeter_, and _Delphinus_ occur in the Older Pliocene of England and France, and with these the remains of many extinct forms, _Balænodon_ and _Hoplocetus_ (Balænidæ); _Belemnoziphius_ and _Choneziphius_ (Hyperoodontidæ), and _Halitherium_, an extinct form of the next order--Sirenia, now confined to the tropics, although the recently extinct _Rytina_ of the N. W. Pacific shows that it is also adapted for temperate climates. _Ungulata._--The Pliocene deposits are not very rich in this order. The horses (_Equidæ_) are represented by the genus _Equus_; and here we first meet with _Hipparion_, in which small lateral toes appear. Both genera occur in British deposits of this age. {113}A more interesting fact for us is the occurrence of the genus _Tapirus_ in the Newer Pliocene of France and in the older beds of both France and England, since this genus is now isolated in the remotest parts of the eastern and western tropics. The genera _Rhinoceros_, _Hippopotamus_, and _Sus_, occur here as in the preceding epoch. We next come to the deer genus (_Cervus_), which appears to have been at its maximum in this period, no less than eight species occurring in the Norwich Crag, and Forest-beds. Among the Bovidæ, the antelopes, ox, and bison, are the only forms represented here, as in the Post-Pliocene period. Passing on to the Proboscidea, we find three species of elephants and two of _Mastodon_ preserved in European beds of this period, all distinct from those of Post-Pliocene times. _Rodentia._--In this order we find representatives of many living European forms; as _Cricetus_ (hamster), _Arvicola_ (vole), _Castor_ (beaver), _Arctomys_ (marmot), _Hystrix_ (porcupine), _Lepus_ (hare), and _Lagomys_ (pika); and a few that are extinct, the most important being _Chalicomys_, allied to the beaver; and _Issiodromys_, said to come nearest to the remarkable _Pedetes_ of South Africa, both found in the Pliocene formations of France.