22 
the other valve which met it when it was young, although now 
far removed. I have a specimen, upon the beak of which 
is the concave impression of a Cardium, and a convex 
impression upon the lid;* their correspondence appears at 
first difficult to understand, but they prove, that Gryphasae 
are no more free shells than Ostreae. The otherwise independ- 
ent appearance of full grown shells, deceived the great and 
discerning Delamarck. The right side is often distinguished 
by an obscure lobe or sulcus. 
These shells seem generally more changed than most pe- 
trified Oysters, and the lamina are less tender and less 
divided. Fragments, however, are often with difficulty 
distinguished from those of Oysters. I do not quite know 
at present that I have received Ostreae from the same stra- 
tum as the ‘Gryphaeae, yet the former are abundant in many 
places. We conceive, that a knowledge of the different spe- 
cies of Gryphsea will be of some importance in identifying 
formations, as they appear to occur in many places. I 
have them in the blue and white Lias ; in the great Oolite, 
particularly in the Clay which intersects its beds ; in the 
Clunch Clay, the Kellaway Limestone, &c. and from the 
following places; Weston, near Bath; Purton Passage- 
ferry, in the mud; Frethern ; Weymouth; Radipole ; 
Kellaway ; Elveston, near Bedford ; Norton-Disney, in 
Lincolnshire; Kettering, in Northamptonshire; Birdbrook, 
in Essex; Strontian, in Argylehire; and Belfast. 
* I have a recent Oyster adhering to a Pecten, which has the impression 
of the ribs of the Pecten through both valves in a similar way, although a 
quarter of an inch or more in depth : also some specimens of Anomia ephip- 
pium of Linrueus, which are larger, (being always an adherent shell, and 
when on the common Oyster not appearing particular) but the ribs or 
striffi being thus formed, gives them a sort of specific difference. I had 
this long since, through the generosity of Miss Pocock, gathered near 
Marazion. 
