244 Mr. Webster on the Strata lying over the Chalk. 



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 whicli 

 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 to 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 fhnts frequently contain alcyonia. 



The Fossil-bones of quadrupeds are frequently found in the allu- 

 vium 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 particu- 

 larly 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 /;/ the 



* A very fine example of one occurs in a specimen in the museum of the Geological 

 Sgciety, presented by Leonard Horner, Esq. It is a small bivalve resembling a pecteu. 



