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trative specimen, in such a situation as shall best allow of its 
examination. 
We have thus seen the same roundish oyster at Plumstead, Wool- 
wich, and Bromley ; but I was not able to find, either at Plumstead 
or at Bromley, the long oyster, the remains of which were discoverable 
at Woolwich. On Bexley Heath, however, about three miles from 
Woolwich, in a south-east direction, a species of oyster is found, at 
two or three feet beneath the surface, in the mould, which seems to 
be similar with that of Woolwich ; and is, at the same time, in a much 
better state of preservation. 
The Bexley oyster is from two to three inches in length, and from 
one to one and a half in breadth. The outer surface is rough. The 
impression is rather large ; and the cartilaginal pit, which is finely 
striated in a transverse direction, is formed on a vaulted surface of 
half or three quarters of an inch in length, beneath which vaulted sur- 
face a part of the animal must have been disposed. 
The shell, which seems, more than all others, to deserve to be termed 
O. fornicata, is one which, from the appearance of the adherent matrix, 
I suspect to have been found on the Hampshire coast. It is about two 
inches in length, and one and a half in breadth. Its outer surface is 
pretty smooth. On its inner surface the margin is seen finely striated, 
concentrically, by the added lamellae of growth. The mark of adhe- 
sion is about the middle of the shell, and there is no appearance of 
any pit. But the circumstance most interesting, in this shell, is a 
vaulted floor, sunk rather more than the eighth of an inch below the 
margin, and extending from the beak to the middle of the shell. 
A part of the animal must, of course, have existed beneath this floor, 
as the mark of adhesion is formed just beneath its edge. 
I have a single valve of an oyster-shell, from Carshalton , which is about 
four or five miles south-west of Bromley ; but this valve is larger, longer, 
and flatter, than those belonging to the shells already described. The 
Carshalton oyster seems to approach much nearer to the form ot the 
