Page:Quarterly Journal of the Geological Society of London, vol. 28.djvu/527

1872.] 3. The third is that the Hippopotamus could not have traversed vast distances, say from the south of France to Kirkdale, in Yorkshire, in one season. So far from holding this view, I have always maintained that in the vast lapse of time represented by the Pleistocene, or, as Mr. J. Geikie, speaking merely from the point of view offered by Scotland, terms it, the "Glacial Period," every inch of ground in Middle Europe was fought over by the invading and retreating forms, not at one time, but at successive times.

4. To the fourth objection (p. 167), that, under the conditions of climate to which I have referred, the vegetation of Britain would have been too scanty and meagre for the support of the animals, and that the destructive floods would reduce the lower grounds to a desert at the break-up of the winter, it is only necessary to refer to Wrangel's 'Siberia,' Middendorf's 'Sibirische Reise,' and Sir John Franklin's 'Overland Journeys,' to prove the existence of a luxuriant forest- vegetation in the region extending in Middle Siberia south of the Tundras, and in that south of the Barren Grounds, and the fact that large floods in the spring do not destroy the vegetation.

5. A further objection is based on the presence in some cases of Unio littoralis and Corbicula consobrina along with the mammalia in the river-deposits. Can we predicate temperature from either of these shells? The former still lives in the Loire; and the latter is abundant in the beds of the streams in the region of the Himalayas. The evidence as to the existing range of both these mollusks does not seem to me sufficient to trace any conclusion as to Pleistocene temperature.

The third group of Pleistocene mammalia (which still inhabits the temperate zones of Europe, Asia, and America (is far larger than either of the preceding which we have described. It contains the

In the Pleistocene this group of animals had very much the same range over Europe as they have at the present time, although many of the species have retreated from their ancient homes. Thus the Grizzly Bear, which then ranged from the shores of the Mediterranean into Great Britain, Central Germany, and Belgium, has retreated to its present stronghold in the Rocky Mountains, And al- though, unlike its more arctic associate in France and Britain, the Musk-sheep, it has not been recognized in European Russia or in Northern Asia, there can be little doubt that its line of retreat was eastwards by the Straits of Behring. The Antilope saiga, which then passed as far to the west as Auvergne, and the Musk-shrew, which has been discovered at Bacton, are now only living in the warmer