Page:Quarterly Journal of the Geological Society of London, vol. 31.djvu/98

52 52 J. PRESTWICH ON THE QUATERNARY PHENOMENA Hope's Nose near Torquay, and then taking a nearly direct line across Bridport Bay to the south end of Portland. Thence, at some distance beyond, it passed more inland, ranging near Fareham and Chichester, to Brighton, and to the Straits of Dover. Up this channel the shingle was drifted, as to a certain extent at present, from the westward, while floating ice transported the larger blocks found in places on the Sussex coast from more distant localities. In the mean time an east and west anticlinal disturbance slowly elevated the Weymouth district, and with it part of the Purbeck and Portland area — succeeded or accompanied by a denudation which not only levelled but deeply channelled the uplifted areas. At the close of this period Portland must have presented nearly the same features as at present, only that the surface was varied by the presence of hills of the Middle Purbeck strata. The final submergence of which we have before spoken, and the subsequent emergence, buried the old cliff and sea-line under the mass of angular debris washed down from the adjacent land (denuding possibly some areas more deeply), and left the district much as we now see it, with its pleasant variety of hill and dale, its well-marked and bold escarpments, and its diversified geological features. Note on the Fossil Shells. By J. Gwtn Jeffreys, Esq., P.R.S. I have examined the shells and washed shell-sand from the raised beach at Portland, collected by Mr. Prestwich. The shells are rather northern than southern ; but but I have not detected any peculiarly arctic species, and certainly none of a Mediterranean or Lusitanian type. All the species inhabit the British coasts from Shetland to Yorkshire, except one, which I consider un described, and propose to name Bissoa subcylindrata. I subjoin a description of this species. Another species (Trochus helicinus) has not, so far as I am aware, been found south of Yorkshire and Dublin Bay. The most northern known locality for another species (Trochus umbili- catus) is Stornoway in the outer Hebrides; and it occurs in a raised beach at Portrush*. The freshwater bed which overlies the raised beach contains very few species of Mollusca. These shells I am disposed to re- gard as northern, although the species have an extensive distri- bution southwards. J. Gwyn Jeffreys. Ware Priory, 9th June, 1874. Bjssoa subcylindrata, Jeffreys. Shell somewhat cylindrical, solid, opaque, glossy: sculpture none, except occasional lines of growth : colour whitish : spire rather short ; apex blunt : whorls 4-5, convex, regularly increasing ; the last to have formed part of a beach or strand in the neighbourhood of rocks.
 * All the shells belong to the littoral zone. The sand and its contents appear