_General Considerations on the Extinct Mammalian Fauna of Europe._--It is a curious fact that no family, and hardly a genus, of European mammalia occurs in the Pliocene deposits, without extending back also into those of Miocene age. There are, {127}however, a few groups which, seem to be late developments or recent importations into the Palæarctic region, as they occur only in Post-Pliocene deposits. The most important of these are the badger, glutton, elk, reindeer, chamois, goat, and sheep, which only occur in caves and other deposits of Post-Pliocene age. Camels only occur in the Post-Pliocene of Siberia (_Merycotherium_), although a true _Camelus_ of large size appears to have inhabited some part of Central Asia in the Upper Miocene period, being found in the Siwalik beds. The only exclusively Pliocene genera in Europe are _Ursus_, _Equus_, _Hippopotamus_, _Bos_, _Elephas_, _Arvicola_, _Trogontherium_, _Arctomys_, _Hystrix_ and _Lepus_; but of these _Equus_, _Hippopotamus_, _Bos_, and _Elephas_ are found in the Miocene deposits of India. Owing, no doubt, in part to the superior productiveness of the various Miocene beds, large numbers of groups appear to have their origin or earliest appearance here. Such are Insectivora, Felidæ, Hyænidæ, Mustelidæ, _Ursus_, Equidæ, _Tapirus_, Rhinocerotidæ, Hippopotamidæ, Anthracotheridæ (extinct), _Sus_, Camelopardidæ, Tragulidæ, Cervidæ, Bovidæ, Elephantidæ, and Edentata. Groups which go back to the Eocene period, are, Primates allied to South American monkeys, as well as some of the Lemuridæ; bats of the living genus _Vespertilio_; Hyænodontidæ, an ancestral form of Carnivore; Viverridæ; Canidæ (to the Upper Eocene), and the ancestral Arctocyonidæ to the Lower Eocene; _Hyænarctos_, an ancestral type of bears and hyænas; Anchitheridæ, ancestral horses, to the Middle Eocene; Palæotheridæ, comprising numerous generalised forms, ancestors of the rhinoceros, horse, and tapir; Suidæ, with numerous generalised forms, to the Middle Eocene; Anoplotheridæ and Xiphodontidæ, ancestral families of even-toed Ungulates, connecting the ruminants with the swine; and lastly, several groups of Rodents, and a Marsupial, in the Upper Eocene. We thus find all the great types of Mammalia well developed in the earliest portion of the tertiary period; and the occurrence of Quadrumana, of the highly specialized bats (_Vespertilio_), of various forms of Carnivora, and of Ungulates, clearly differentiated into the odd and even-toed series, associated with such lower forms as {128}Lemurs and Marsupials--proves, that we have here hardly made an approach towards the epoch when the mammalian type itself began to diverge into its various modifications. Some of the Carnivora and Ungulates do, indeed, exhibit a less specialised structure than later forms; yet so far back as the Upper Miocene the most specialised of all carnivora, the great sabre-toothed _Machairodus_, makes its appearance.