mainder are certainly so--together with the Mammoth and
the Woolly Rhinoceros, which are undoubtedly extinct. Along with
these are found the implements, and in some cases the bones, of
Man himself, in such a manner as to render it absolutely certain
that an early race of men was truly contemporaneous in Western
Europe with the animals above mentioned.

IV. UNCLASSIFIED POST-PLIOCENE DEPOSITS.--Apart from any of the
afore mentioned deposits, there occur other accumulations--sometimes
superficial, sometimes in caves--which are found in regions where
a "Glacial period" has not been fully demonstrated, or where
such did not take place; and which, therefore, are not amenable
to the above classification. The most important of these are
known to occur in South America and Australia; and though their
numerous extinct Mammalia place their reference to the Post-Pliocene
period beyond doubt, their relations to the glacial period and
its deposits in the northern hemisphere have not been precisely
determined.

CHAPTER XXII.

THE POST-PLIOCENE PERIOD--_Continued_.

As regards the _life_ of the Post-Pliocene period, we have, in
the first place, to notice the effect produced throughout the
northern hemisphere by the gradual supervention of the Glacial
period. Previous to this the climate must have been temperate or
warm-temperate; but as the cold gradually came on, two results were
produced as regards the living beings of the area thus affected.
In the first place, all those Mammals which, like the Mammoth, the
Woolly Rhinoceros, the Lion, the Hyaena, and the Hippopotamus,
require, at any rate, moderately warm conditions, would be forced
to migrate southwards to regions not affected by the new state
of things. In the second place, Mammals previously inhabiting
higher latitudes, such as the Reindeer, the Musk-ox, and the
Lemming, would be enabled by the increasing cold to migrate
southwards, and to invade provinces previously occupied by the
Elephant and the Rhinoceros. A precisely similar, but more
slowly-executed process, must have taken place in the sea, the
northern Mollusca moving southwards as the arctic conditions of
the Glacial period became established, whilst the forms proper
to temperate seas receded. As regards the readily locomotive
Mammals, also, it is probable that this process was carried on
repeatedly in a partial manner, the southern and northern forms
alternately fluctuating backwards and forwards over th