1840.] 



On the Geology of Ctitch, 



Pecten Somi^owensin, Obovate, convex, radiated ; radii about 24, 

 squamose, subdivided, in one valve into 3, in the other into 5 : ears un- 

 equal, striated, and squamose. Length 2 inches 2 lines, width nearly 2 

 inches. 



In form this Pecten approaches to P. variaiis, but in the structure of 

 the surface it is like P. plebeius of the Crag, and many recent species. 

 Loc. Soomrow. 



Pecten articulatus. Orbicular, with pointed beaks, depressed, radia- 

 ted ; radii about 28, simple, rounded, crossed by distant scales ; ears 

 large, striated, and squamose. Length in an old specimen about 1 inch 

 8 lines, width 1 inch 6 lines. 



The radii when the scales are worn off appear jointed. 



Loc. Bank of the Runn. 



Gryphcea glohosa, (M. C. t. 392, Osti^ea vesicularis, Lam, Hist. Nat. 

 vol. vi. part I. p. 219. Cuv. and Brongn. Env. de Paris, 383, t. 3. f. 5. 



Podopsis gnjph(Soides, Lam. Hist. Nat. vol. vi. parti. 195). 



This exactly agrees with old specimens found in the chalk of Norfolk, 

 Loc. Kotra. 



Ostrea avgulata. Suborbicular, arched, compressed, plaited; plaits 

 angular, numerous, branched towards the margin ; laminae of increase 

 regular, distant, raised at their edges. Length about 1| inch, width the 

 same. 



Loc. Kotra. 



Ostrea Flabelhdum, (M. C. t. 253 Lam. Hist. Nat. vol. vi. part 1. 215. 

 Chama plicata, Brander, 84 and 85.). The identit}'- of this oyster with 

 the O. Flahellulum of the tertiary formations of Europe is unquestiona- 

 ble. 



Loc. Cheeosir. 



Ostrea tubifera. Orbicular ; laminae of increase thick, raised into a 

 few large, nearly erect tubes arranged in about 6 rows. Diameter 2 

 inches, 



Loc. 



Ostrea Lingua. Much elongated, smooth, approaching to even ; up- 

 per valve flat or concave, the other very convex ; squamoso-fimbriated 

 at the edges. Length 2| inches, width 1^ inch. 



So variable are Ostrea in form and so much do the species resemble 

 each other, that it is hardly possible to define some of them clearly. 

 That before us is very like O. tenera (M. C. t. 252, f. 2 and 3.), yet in 



