EXPLANATION OF THE PLATES AND WOOD-CUTS. 



Fig. 12. Area radiata. Transversely elongated, oblique, rather convex, radiated ; 

 radii elevated, furrowed ; beaks almost close, nearest the anterior side. 

 Length 7 lines, width 1 inch. 

 Loc. Soomrow. 

 Fig. 13. Area tortuosa ? Linn. This is only a fragment, and what there is, seems to 

 differ from the recent Area tortuosa in the degree of curvature. 

 Loc. Soomrow. 

 Fig. 14. Peeten Somrowensis. Obovate, convex, radiated ; radii about 24, squamose 

 subdivided, in one valve into 3, in the other into 5 ; ears unequal, striated, and 

 squamose. Length 2 inches 2 lines, width nearly 2 inches. 



In form this Peeten approaches to P. varians, but in the structure of the sur- 

 face it is like P. plebeius of the Crag, and many recent species. We have given 

 a magnified figure of part of the surface of the opposite valve. 

 Loc. Soomrow. 

 Fig. 15. Peeten artieulatus. Orbicular, with pointed beaks, depressed, radiated; 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. 

 We have figured a small specimen. 



The radii when the scales are worn off appear jointed. 

 Loc. Bank of the Runn- 

 Fig. 16. Gryphcea globosa, (M. C. t. 392. Ostrea vesieularis, Lam. Hist. Nat. Vol. vi. 

 part 1. p. 219. Cuv. and Brongn. Env. de Paris, 383, t. 3, f 5. Podopsis gry- 

 phcBoides, Lam. Hist. Nat. Vol. vi. part 1. 195.) 



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

 Loc. Kotra. 

 Fig. 17. Ostrea angulata. Suboi'bicular, 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. 

 Fig. 18. Ostrea Flabellulum, (M. C. t. 253. Lam. Hist. Nat. Vol. vi. part 1. 215. Chama 

 plieata, Brander, 84 and 85.). The identity of this oyster with the O. Flabellu- 

 lum of the tertiary formations of Europe is unquestionable. 

 Loc. Cheeosir. 

 Fig.ld. Ostrea tubif era. Orbicular; laminae of increase thick, raised into a few large, 

 nearly erect tubes arranged in about 6 rows. Diameter 2 inciies. 

 Loc. 

 Fig. 20. Ostrea Lingua. Much elongated, smooth, approaching to even ; upper valve 

 flat or concave, the other very convex ; squamoso-fimbriated at the edges. Length 

 2| inches, width li inch. 



So variable are Ostrecs 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 the depth of the attached valve it 

 approaches to O. Meadii (M. C. 252, f. 1 and 4.), but is not waved like that. 

 Loc. near Joonagrea and Kotra. 



