121 
OSTREA Bellovacina. 
TAB. CCCLXXXVlil. —Fig. 1 and 2. 
Spec. Char. Thick, oblong, wedge-shaped, 
front rounded ; lower valve convex, com- 
posed of undulating laminae, the other flat 
and plain. 
Syn. O. Bellovacina, ? Lam . Annales du Mus . 
VIII. p. 159. XIV. t. 20. f. 1. Hist. Nat. 
VI. pt. 1, 218. 
A s usual with irregular shells ; there are hardly two 
specimens of this Oyster of the same form ; it varies 
from nearly orbic* lar to wedgeshaped ; generally how- 
ever, having the beak produced with a straight line on 
each side of it ; the depth of the hollow valve is seldom 
considerable, both valves are thick and strong, but not 
remarkably so for the size of the shell ; and it appears to 
be of quick growth ; the area to which the hinge ligament 
was attached, is somewhat elevated above the surface of 
the shell ; in the hollow valve it is curved and pointed, 
and has a deep canal in the middle ; the length is about 
5 inches. 
Many single valves of this Oyster are to be found 
scattered through the uppermost beds that contain fossil 
shells, in the Great Sandpit between Charlton and 
Woolwich, they are among gravel accompanied by 
Cyclades, Potamides, Neritae, and Melanopsides in 
abundance and rarely by Mytili and Arcae. It does not 
appear to me to be the same species as the Oyster found 
close to the Chalk at Reading, as some Geologists have 
supposed ; neither am I aware that the same species is 
found in the upper Marine stratum on the Isle of Wight, 
to which the accompanying shells would seem rather to 
refer the stratum in which it occurs at Woolwich. There 
is a very peculiar circumstance to be observed in such 
specimens as have been in contact with pebbles ; there 
are hollows worn deep in their substance, in which the 
pebbles are imbedded, frequently without cracking the 
shells, although sometimes the shell is cracked and bent 
over a large pebble, as if the mass of gravel had been at 
