_Pleistocene or Post-Pliocene Period._--We first meet with proofs of important changes in the character of the European fauna, in studying the remains found in the caverns of England and France, which have recently been so well explored. These cave-remains are probably all subsequent to the Glacial epoch, and they all come within the period of man's occupation of the country. Yet we find clear proofs of two distinct kinds of change in the forms of animal life. First we have a change clearly traceable to a difference of climate. We find such arctic forms as the rein-deer, the musk-sheep, the glutton, and the lemming, with the mammoth and the woolly rhinoceros of the Siberian ice-cliffs, inhabiting this country and even the south of France. This is held to be good proof that a sub-arctic climate prevailed over all Central Europe; and this climate, together with the continental condition of Britain, will sufficiently explain such a southward range of what are now arctic forms. But together with this change we have another that seems at first sight to be in an exactly opposite direction. We meet with numerous animals which now only inhabit Africa, or South Europe, or the warmer parts of Asia. Such are, large felines--some closely related to the lion (_Felis spelæa_), others of altogether extinct type (_Machairodus_) and forming the extreme development of the feline race;--hyænas; horses of two or more species; and a hippopotamus. If we go a little further back, to the remains furnished by the gravels and brick-earths, we still find the same association of forms. The reindeer, the glutton, {111}the musk-sheep, and the woolly rhinoceros, are associated with several other species of rhinoceros and elephant; with numerous civets, now abundant only in warm countries; and with antelopes of several species. We also meet here with a great extension of range of forms now limited to small areas. The Saiga antelope of Eastern Europe occurs in France, where wild sheep and goats and the chamois were then found, together with several species of deer, of bear, and of hyæna. A few extinct genera even come down to this late period, such as the great sabre-toothed tiger, _Machairodus_; _Galeotherium_, a form of Viverridæ; _Palæospalax_, allied to the mole; and _Trogontherium_, a gigantic form of beaver,