10 



Broccbs and Lamarck (manifested by the remains being 

 "wholly pearly,) are 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 

 iigured. 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 Sandfoot 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, 

 longitudinaliy ribbed, rather thick, smooth. 



^Nearly 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 Avidth : a consider- 

 able portion of the shell is pearly. 



Very abundant in the sandstone of the Bognor Rocks, 

 where it is accompanied by an Anomia, similar to one 

 commonly attached to the recent Pinna ingens. It has 

 also been found at Mighgate in Septaria composed of 

 sandy Marie. 1 suspect Lamarck's P. margaritacea 

 juay be the same species deprived of its fibrous coat. 



PINNA arcuata. ' 



TAB. €CCXIII.— 1^*^. 3. 



Spec. Char. Nearly equilateral, ventricose, 

 finely ribbed, arched. 



Nearly 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, 

 I cannot but consider if a distinct species : it appears td 

 fee quite different iVum V. iruiuvu i>f Linn, : it occurs in 

 Septaria. 



