Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/204

From Wikisource
Jump to navigation Jump to search
This page has been validated.
Mr. Webster on the Strata lying over the Chalk.

This ingenious and indefatigable collector has also lately ascertained a number of fossil bodies found among them to be the excrescences produced by insects on the branches of various trees; and I have been since favoured by him with a portion of the jaw of a crocodile found in Sheppey; a fossil extremely interesting, since it is the only instance yet observed of the bones of this animal having been found in the London clay.

Almost the whole of the vegetable and animal remains are entirely impregnated with sulphuret of iron, and the vestiges of shells are chiefly casts in this substance. The quantity of fragments of pyritous branches[1] and fruits is very great.

Among the pyritous casts of shells I found one that much resembled the lymneus, and another the planorbis, but too imperfect to decide the species. It is proper however to mention, that in a late number of the Journal de Physique, in a paper on freshwater shells by M. Braarde, mention is made of three freshwater shells from Sheppey, the lymneus, melania, and nerita.

These shells however, which are very few in number, do not prove the existence of a freshwater formation in this place similar to those of the basins of Paris and of the Isle of Wight: being found among the remains of vegetable and of marine animals, we may suppose that they were carried down together with the branches of trees and fruits by the numerous streams and rivers that must have flowed into this gulph.

Most of the best preserved organic remains are enclosed in the

  1. It will be an interesting investigation for the experienced botanist to trace the living analogues of these ancient productions of this part of the earth. Such of them as have been recognised are found to belong to species now growing only in the torrid zone; thus adding to the evidence afforded by the animal remains of the great change that must have taken place in the climate.