The prehistoric fauna is distinguished from that of the pleistocene not merely by the appearance of the animals above mentioned, which were hitherto unknown, but by the absence of many species which were living during the latter period. The cave bear, woolly rhinoceros, and mammoth, for example, became extinct, the musk-sheep and lemming were banished from a temperate latitude to take refuge in the regions of the north, while the spotted hyæna, the hippopotamus, and Felis caffer, retired to the warm regions of Africa, where they are still living. _The Archæological Classification._ The prehistoric period has been classified by the archæologists according to the stages of human progress which it presents. At the frontier of history, in each country, we find that the dwellers were acquainted with the use of iron, and had found it to be the most convenient material for the manufacture of cutting weapons and implements. Before this the voice of tradition points out that bronze was the only material used for these purposes, and stone before bronze. These three stages of human culture, or the ages of iron, bronze, and stone, have been fully verified by investigations which have been made in various parts of Europe, into the prehistoric habitations and burial-places of man. This classification by no means implies an exact chronology, or that any one of these ages, with the exception perhaps of the first, covered the whole of Europe at the same point of time, but that the order in which they followed each other is the same in each country which has been explored. There is good reason for the belief, that at the time the Egyptian and Assyrian empires were in the height of their glory, Northern Europe was inhabited by rude polished-stone-using races. And it is a well-ascertained fact, that while the inhabitants of Britain and Scandinavia were in their bronze age, the Etruscans and Phœnicians were in their full power in the south. It is obvious again, that, even in the same country, the poorer classes must have been long content to use the ruder and more common materials for their daily needs, while the richer and more powerful used the rarer and more costly. These three ages must therefore necessarily overlap. “Like the three principal colours of the rainbow,” writes Mr. Evans,[87] “these three stages of civilization overlap, intermingle, and shade off the one into the other; and yet their succession, as far as Western Europe is concerned, appears to be equally well defined with that of the prismatic colours, though the proportions of the spectrum may vary in different countries.” They cannot reasonably be viewed as hard and fast lines of division, mapping off successive quantities of time.