Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/635

Rh chalk-flints from neighbouring shores shows transport by ice. The many fragments of secondary rocks and of mountain-limestone in the Red and Norwich Crags were probably brought down by river-action or river-ice. Nor is the increase in the northern species of shells very great in ascending through the Norwich Crag, though the number of individuals increases considerably, and a number of southern species become extinct. At the same time it is singular that so many Coralline-Crag species, mostly of British and Mediterranean forms, should reappear in the last or uppermost stage of the Crag at Aldeby.

This conclusion is in accordance with the land-fauna and flora we find flourishing subsequent to the Norwich Crag. The winter cold may have been greater; but otherwise the climate seems to have been a moderately temperate one. In the Forest-bed the vegetation, whether as regards the species or the size of the trees, is far from indicating a severe climate. Nor do we find any of the Mammalia which indicate extreme cold. The Mastodon no longer appears; but an Elephant, a Bear, and two Deer of the Crag period survive. With these, however, some of the animals of the postglacial period appear, showing probably the setting in of colder conditions there or further north. In the Westleton shingle we get the drifted remains of the same vegetation, and the same land and freshwater shells; but these latter are of a character common to all northern and temperate Europe. The marine Molluscan fauna now becomes poorer, but still without any decidedly marked northern characters; nor are any foreign boulders found—nothing but drifted pebbles carried possibly along a shore-line. Nevertheless we have in this series the nearest known approach to the glacial period, which set in immediately afterwards with a rigour and intensity denoting, I apprehend, causes of an entirely different order from those, the effects of which, up to this time, may be attributed to the known and assignable influence of land configuration and oceanic currents.