76 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Dec. 18,
of basis for argument. The beds thinned out to the west and thickened to the east. He was prepared to accept the two lobster-beds,
which in the section were one over the other, as merely showing the
persistence of the same bed, which, though continuous, had changed
its position during the interval.
Prof. T. Rupert Jones considered that certain beds in the Wealden were susceptible of correlation over very wide areas by means of certain brecciated beds. He pointed out that near Pulborough and at other places the Wealden terminated in paper shales, the same as those which Mr. Meyer had placed at the top of the series at Punfield. Above these he thought no purely freshwater beds were to be found. He considered that the whole, including the Wealden, were included in the Neocomian.
Mr. Etheridge thought the difference between the various writers on this subject to be mainly one of terms. The same fossils as those found at Punfield had been found in abundance in Spain.
Mr. Meyer maintained, in opposition to Mr. Judd, that the Punfield beds were not merely Upper Wealden. He had found a certain form of Ostrea over large areas always on the same horizon; and this had occurred at Punfield at precisely the level at which, in accordance with his views, it ought to have been present. Above the marine bands he had sought in vain for freshwater fossils.
2. On the Coprolites of the Upper Greensand Formation, and on Flints. By W. Johnson Sollas, Esq., Associate of the Royal School of Mines, London; Scholar of St. John's College, Cambridge.
(Communicated by the Rev. T. G. Bonney, M.A., F.G.S.)
[Abstract.]
Part I.
The first part of this paper was principally occupied in an endeavour to explain the perfect fossilization of sponges and other softbodied animals. It was shown that the hypothesis which considered that sponges had become silicified by an attraction of their spicules for silica was altogether untenable. Mr. Hawkins Johnson's supposititious reaction, according to which the carbon of animal matter is directly replaced by silicon, was shown to be inconsistent with the known facts of chemistry. The author's explanation was not intended to be final. The first fact pointed out was the very remarkable way in which the silica or calcic phosphate of the fossils under consideration followed the former extension of organic matter. This was explained for silica by the fact that, when silicic acid is added to such animal matters as albumen or gelatin, it forms with them a definite chemical compound; and it was assumed that in process of time this highly complex organic substance would decompose, its organic constituents would be evolved, and its silica would remain behind. In such a way flints might be produced, and dialysis would lend its aid. The same explanation was applied to account for the connexion
