Page:A Treatise on Geology, volume 1.djvu/339

 CHAP. VI. turritella terebra, murex erinaceus, and cardium edule, are covered by the ordinary sandy diluvium of Cheshire, in which are many erratic blocks from the North of England, as well as pebbles from the Welsh border.

In and near the valley of the Ribble, for some miles inland, from its mouth, near Blackpool, by Preston to the base of Longridge fell, and on Whittle hills, from the level of the sea to 300 feet above it, occur beds of marl, sand, and gravel, under the ordinary diluvium with erratic blocks, locally full of shells of mollusca now living on the neighbouring coast—such as turritella terebra, cardium edule, tellina solidula, &c. The lamination of these shelly beds is irregular, resembling a modern beach accumulated under the influence of strong currents.

Somewhat different appearances are seen in the opposite parts of Yorkshire, especially in the district of Holderness, where sandy and gravelly beds, full of pebbles and fragments of Cumbrian rocks, contain, at particular spots (Brandsburton, Paul, Ridgmont), layers of shells, all marine, and all, except one, now living in the neighbouring seas. Besides the strong shells of turbo littoreus, purpura lapillus, and buccinum undatum, we have mya arenaria, teilina solidula, t. tenuis, mactra subtruncata, cardium edule, &c.; and it is certainly very strange to discover these and other tender shells in a good state of conservation among the twisted and confused laminæ of so coarse and irregular a deposit as that in the vicinity of Ridgmont.

On the same coast, at Speeton, is a much more regular sandy deposit full of cardium edule, amphidesma Listeri, tellina solidula, &c., on the top of the cliff.

From the Wexford coast of Ireland, Mr. Griffith produced at the Dublin meeting of the British Association, shells of existing, and also of extinct, species, from what seemed a raised beach. A similar deposit, on a very extensive scale, occurs on the coasts of North and South Devon and Cornwall. (Murchison, Sedgwick, De la Beche, &c.)