sented in Britain. The spotted hyæna, lion, lynx, Caffer cat, and hippopotamus, have taken refuge in the southern climates; the lemming, glutton, pouched marmot, musk sheep, and tailless hare, have retreated either to the north, or to the shelter offered by the forests of Central Europe, or the tops of lofty mountains; while the cave-bear, woolly rhinoceros, leptorhine rhinoceros, mammoth, and straight-tusked elephant (E. antiquus), have become extinct. On the other hand, it may be concluded from the fact that all the wild Prehistoric mammals were living in the preceding age, that the Prehistoric period is not cut off from that which went before by a line of demarcation such as that dividing the Secondary from the Tertiary periods. The wild fauna and flora of Prehistoric and Historic Europe may be traced back to the Pleistocene age, and therefore the Tertiary period must be looked upon as not ending with the Pleistocene, but as extending down to the present day (see Fig. 1).
Magnitude of Interval between the Pleistocene and Prehistoric Periods.
Such changes in the mammalia and in the geography of Britain as those described in the preceding pages, in the interval separating the Pleistocene from the Pre- historic period, could not have taken place in a short time, and when we reflect that comparatively little change has taken place in this country during the last two thousand years, it is obvious that the one period is separated from the other by the lapse of many centuries. Of how many we cannot tell. The sharp line of demarcation between the two is to be noticed in almost every
