121 



OSTREA Bellovacina. 

 TAB. CCCLXXXVllL— i^z^. 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, ' JLam. Annales du Mus. 

 VlILp. 159. XIV. t. 20. f. 1. Hist. Nat. 

 Vl.pt. 1, 218. 



As usual with irregular shells ; there are hardly two 

 specimens of this Oyster of the same form ; it varies 

 from nearly orbicular 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 specitsis 

 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 



