The geographical distribution of animals, with a study of the relations ...

chap, vi.] MAMMALIA OF THE OLD WORLD. Illthe musk-sheep, and the woolly rhinoceros, are associated withseveral other species of rhinoceros and elephant; with numerouscivets, now abundant only in warm countries ; and withantelopes of several species. We also meet here with a greatextension of range of forms now limited to small areas. TheSaiga antelope of Eastern Europe occurs in France, where wildsheep and goats and the chamois were then found, together withseveral species of deer, of bear, and of hysena. A few extinctgenera even come down to this late period, such as the greatsabre-toothed tiger, Machairodus ;Galeotheriurn, a form of Viverridse; Palceospalax, allied to the mole ; and Trogontherium, agigantic form of beaver.We find then, that even at so early a stage of our inquiries wemeet with a problem in distribution by no means easy to solve.How are we to explain the banishment from Europe in so shorta space of time (geologically speaking) of so many forms of lifenow characteristic of warmer countries, and this too during aperiod when the climate of Central Europe was itselfbecomingwarmer ? Such a change must almost certainly have been dueto changes of physical geography, which we shalltobe better ableunderstand when we have examined the preceding Plioceneperiod. We may here notice, however, that so far as we yetknow, this great recent change in the character of the fauna isconfined to the western part of the Palaearctic region.In cavesin the Altai Mountains examined by Prof. Brandt, a great collectionof fossil bones was discovered. These comprised theSiberian rhinoceros and mammoth, and the cave hysena ;but allthe others, more than thirty distinct species, are now living inor near the same regions. We may perhaps impute this differenceto the fact that the migration of Southern types intothis part of Siberia was prevented by the great mountain anddesert barrier of the Central Asiatic plateau ;whereas in Europethere was at this time a land connection with Africa. PostpHocenedeposits and caverns in Algeria have yielded remainsresembling the more southern European types of the Postplioceneperiod, but without any admixture of Arctic forms;showing, as we might expect, that the glacial cold did not