XII.—Notices and Extracts from the Minute-Book of the Geological Society.

Abstract

1.— On the Iron-Sand Formation of Sussex. By Gideon Mantell, Esq. F.R., L., and G. S.S. In the Letter to Dr . Fitton, Secretary of the Geological Society . [Read June 14th, 1822.] Sir, A Short time since I had the honour of presenting to the Society a series of specimens, illustrative of the physical characters and organic remains of the strata of Tilgate Forest. I now submit to its notice some additional examples of the fossils of those deposits, and beg to offer some further observations on their geological position and relations. In my work on the Geology of Sussex, I have mentioned the difficulties which attended the determination of their geognostic position, and the reasons which led me to consider them as related to the Purbeck limestone; but a more accurate survey of the district in which they occur, made in company with my friend Charles Lyell, Esq., Sec. G.S., &c. has enabled me to ascertain that such an opinion is not tenable, and that these strata may with greater propriety be associated with the subordinate beds of limestone, sandstone, and clay, which, in certain parts of Sussex, alternate in the iron-sand formation. In the present state of our knowledge, it may be convenient to separate the strata under consideration into two divisions; comprising in the first the Ashburnham limestone, and in the second, the strata of Tilgate Forest, as in the following tabular arrangement. | | Subdivisions. | Organic Remains. | Localities. | |:------------------- | --------------------------------------------- | ---------------- | ----------- | | 1. Ashburnham beds. | Beds of argillaceous limestone and shale. . . | | |