Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/365



In another fossil of this stratum, a still more extraordinary deviation exists. This fossil possesses the concamerations and the foliaceous sutures of the cornu ammonis; but instead of being spirally coiled, it has its ends turned towards each other, somewhat in the form of a canoe. This peculiar form has led to the placing of this fossil under a separate genus, which has been named Scaphites.

Of the extent of this stratum no correct account has been given; but there is sufficient reason for believing that it accompanies the other chalk in its range through this island. It also appears that its peculiar fossils exist in it at very considerable distances. Thus the oval ammonite, which is found in the Sussex hills, likewise occurs in the hard chalk of Wiltshire; and the scaphites, another inhabitant of the Sussex hills, has also been discovered in Dorsetshire.

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ON comparing the preceding sketch with the Essay on the Mineralogical Geography of the Neighbourhood of Paris, by Messrs. Cuvier and Brongniart, some important variations will be perceived between the strata found above the chalk in this island and in France. In France, the strata above the chalk differ both in number and quality from those which have been hitherto observed in a similar situation in England. In France too, several strata of sand and sandstones exist above the strata of the gravel formation, which in this island appear to be highest.

The first of these differences appears to result chiefly from the existence of numerous beds or patches, the formation of which must have depended on certain local circumstances, such as the existence of fresh or salt water lakes, at the period of the drying up of a former ocean; the different chemical combinations which might thence have taken place, &c. But the occurrence of such