belonged to the chalk strata, but Mr. Parkinson is of opinion that some differences are observable between these echini and those of the chalk. M. Desmarets has described in the lower gypsums of Montmartre fossils similar to those of Grignion, many of which are echini of the genus spatangus, but different from the spatangus cor anguinum found in the chalk. At Grignion too, there are echini which belong no the genus clypeastra.
Impressions of organic remains very rarely occur in the concentric pebbles, particularly those of the Hertfordshire pudding-stone; but the yellow calcedonic flints frequently contain alcyonia.
The Fossil-bones of quadrupeds are frequently found in the alluvium of this part of England, and they appear to be of several dates.
The most ancient are entirely petrified, and where found in the gravel, appear to have been washed out of the strata in which they were originally imbedded, which, from the part of the matrix still adhering to them, appears to have been calcareous. Mr. Parkinson has described some of those found at Walton and Harwich, which however were too much broken to enable him to ascertain distinctly the animal to which they belonged, but he conjectures them to be parts of the Mastodon of Cuvier.
The next class contains the bones of the elephant, rhinoceros, hippopotamus, and the Irish elk, which are no longer natives of this climate. These however are not petrified, and though generally in a state of decay yet are sometimes quite perfect. They are particularly abundant in Suffolk and Norfolk; but have also been found at Brentford, in the Isle of Sheppey, and several other places. And it is particularly important to remark that these are never found in the
- A very fine example of one occurs in a specimen in the museum of the Geological Society, presented by Leonard Horner, Esq. It is a small bivalve resembling a pecten.