10 
Rrocehi and Lamarck (manifested by the remains being' 
wholly pearly,) arc still more extensive in the one 
before us, which is only an imperfect cast in sand 
mixed with a small portion of Mica, the carinated form 
of the valves may arise from pressure, since recent spe- 
cimens are very apt to break in that direction, and 
almost every fossil Pinna has more or less of that form : 
hence the doubts that exist respecting the identity of 
the two species above quoted, neither of which is 
figured. The subject of my figure was sent me from 
Devizes by Mrs. Gent. I have another cast in sand 
probably of the same Pinna, from Sarulfoot Castle, on 
the Isle of Wight, upon which some of the shell re- 
mains. I am indebted to Miss Benett for it. 
PINNA affinis. 
TAB. CCCXIIL— Fig. 2. 
Spec. Char. Cuneiform, ventricose, straight, 
longitudinally ribbed, rather thick, smooth. 
NT early related to P. ingens, but shorter, smoother, 
and thicker : the ribs are small, but slightly elevated, 
and disappear near the edge opposed to the hinge : the 
length is not much greater than the width : a consider- 
able portion of the shell is pearly. 
'Very abundant in the sandstone of the Bognor Rocks, 
where it is accompanied by an Anemia, similar to one 
commonly attached to the recent Pinna ingens. It has 
also been found at Highgate in Septaria composed of 
sandy Marie. I suspect Lamarck’s P. margaritacea 
may be the same species deprived of its fibrous coat. 
PINNA arcuata. 
TAB. CCCXIIL— Fig. 3. 
Spec. Char. Nearly equilateral, ventricose, 
finely ribbed, arched. 
Ni early as deep as long ; the hinge line is gently 
curved ; the opposite edge much arched ; in other res- 
pects this strongly resembles the last. 
Having several specimens of this arched Pinna from 
Highgate exactly alike, as well in curvature as size, 
J cannot but consider it a distinct species : it appears to 
be quite different from P. incurva of Linn. : it occurs in 
Septaria. 
