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was better acquainted with the chamber that lies directly over head, if I may so speak, with but a thin floor between, than with any other in the erection. I had been laboring for years in the Lower Old Red Sandstone, and had acquainted myself with its winged and plate-covered, its enamelled and tubercleroughened ichthyolites; but there is no getting down in Scotland into the cellarage of the edifice: it is as thoroughly a mystery to the mere Scotch geologist as the cellarage of Todgers' in Martin Chuzzlewit, of which a stranger kept the key, was to the inmates of that respectable tavern. Here, however, I had got fairly into the cellar at last. The frontage of fossiliferous grauwacke-looking rock, by the way-side, which I had just examined, is known, thanks to Sir Roderick Murchison, to belong to the Upper Ludlow deposit,—the Silurian base on which the Old Red Sandstone rests; and I had now got a story further down, and was among the Aymestry Limestones.

The first fossil I picked up greatly resembled in size and form a pistol-bullet. It proved to be one of the most characteristic shells of the formation,—the Terebratula Wilsoni. Nor was the second I found—the Lingula Lewisii, a bivalve formed like the blade of a wooden shovel—less characteristic. The Lingula still exists in some two or three species in the distant Moluccas. There was but one of these known in the times of Cuvier, the Lingula anatina; and so unlike was it deemed by the naturalist to any of its contemporary mollusca that of the single species he formed not only a distinct genus, but also an independent class. The existing, like the fossil shell, resembles the blade of a wooden shovel; but the shovel has also a handle, and in this mainly consists its dissimilarity to any other bivalve: a cylindrical cartilaginous stem or foot-stalk elevates it some three or four inches over the rocky base