The prehistoric mammalia consist, as we have seen (p. 136), with the solitary exception of the Irish elk, of the wild animals at present living in Europe, together with the domestic species and varieties introduced by man, probably from central Asia. In the rest of this work we shall have to deal, not merely with the wild animals at present inhabiting Europe, but also with those which have either become extinct, or have migrated to Asia, America, or Africa. Besides this addition to the European fauna in the pleistocene age, the total absence of the domestic animals is a most important feature. The dog, goat, sheep, Celtic short-horn, and domestic swine are conspicuous by their absence: the reputed association of their remains with those of the pleistocene mammals being due, in all the cases which I have examined in France and Britain, to a confusion between distinct strata in the same cave or river-deposit, which are respectively of pleistocene and prehistoric or historic ages. Thus in the excavations in the gravel underneath London, the Celtic short-horn and goat of the superficial strata are very generally mixed with the reindeer and mammoth of the pleistocene gravels below, by the collectors, and the names of the domestic animals have crept into the pleistocene lists. None of the domestic animals have been recorded from any carefully explored strata of that age in any part of Europe. The following late pleistocene species were unknown in Britain in the prehistoric age:-- Glutton. Spotted hyæna. Panther. Lion. Lynx. _Felis Caffer._ Musk-sheep. Bison. Hippopotamus. Lemming. Pouched marmot. Tailless hare. _Lepus diluvianus._ _Arvicola Gulielmi._ Cave-bear. _Rhinoceros hemitœchus._ _R. tichorhinus._ _Elephas antiquus._ Mammoth. The glutton, lynx, bison, and lemming, still live in Europe, the spotted hyæna, _Felis Caffer_, and hippopotamus are peculiar to Africa, the lion to Africa and Asia, and the last seven species are extinct. The _Machairodus cultridens_ and _Rhinoceros megarhinus_ probably disappeared in an early stage of the pleistocene. It may reasonably be inferred, from the migration and extinction of so many species between the close of the pleistocene and beginning of the historic period, that the interval was of considerable length; for it would be impossible for such changes to have taken place in a short time.