Another series of beds, comprising those which are raised a considerable height above the sea, contain a congeries of mixed shells, often broken, and clearly, as we shall show presently, not in sitû; sometimes the shells are imbedded in sand and sometimes in clay. They contain generally a larger proportion of species, and belong to a more temperate condition of things. The fact that Arctic shells are found in these higher beds is undoubted; but, as I contend, the meaning of this is very different to what is often supposed,—the proportion of purely Arctic shells being by no means large, and under any circumstances the mollusca clearly pointing to a condition of things very different indeed to that which must have existed when the great boulder heaps of Smaland and Finland, which I have travelled across for scores of miles with amazement, were being fashioned,—when our azoic Boulder-clays were being manufactured, and when the mollusca which prevail in high latitudes were driven far to the south, to the Mediterranean and elsewhere, where a few of their descendants are still found in very deep water and sporadically.