FROM THE INFERIOR OOLITE. 529 



teeth enclosing a groove, and one large posterior lateral tooth on 

 the left valve. Ligament exterior ? Lunnle undefined. Margins 

 slightly concave in front of the umbo, very convex anteriorly and at 

 the infero-posterior angle, straight below, and oblique posteriorly. 

 Surface flattened centrally, but becoming suddenly steep near the 

 margins, covered with numerous close, concentric, indefinite strise or 

 growth-lines. An obtuse angle runs from the umbo to the infero- 

 posterior corner. Edges smooth within. Structure very thin, except 

 at the margins, which are thickened. 



Dimensions. Length 3| lines, breadth 6 lines, depth 3 lines for 

 both valves. 



This shell, of which I have a single specimen from the Humph- 

 riesianus-zojie of Bradford Abbas, is very similar to Gouldia ? ovcdis, 

 but is thinner and more transverse, and has a more prominent ubmo 

 and a smooth straight inferior edge. From Cardita Moreana, Buv. 

 Geol. Meuse, t. 15. fig. 29, it differs by the presence of a posterior 

 tooth. 



Cypricardia filoperta, n. sp. Plate XVIII. figs. 19, 19 a. 



Shell small, transverse, flatly convex, subquadrate. Umbones 

 rather small, but well defined and prominent, proximate, anterior 

 (being two thirds the diameter from the rear) slightly curving ante- 

 riorly. Lunule small, ovate, deep. Escutcheon very narrow, long 

 and lanceolate. Hinge-line oblique, long and straight. Anterior 

 side narrow and very regularly convex. Inferior and posterior 

 margins crenulated within, very slightly convex, and meeting each 

 other at a highly curved corner, to which point an indistinct oblique 

 angle runs down the shell from the umbo, behind which the surface 

 is slightly concave. The whole surface covered with exceedingly 

 numerous, regular, acute, prominent, threadlike, concentric lines, of 

 almost the same size, from umbo to margin, and with a few greater 

 undulations beneath them. Shell-structure extremely thick, pro- 

 bably half the mass of the fossil being composed of the shell. Valves 

 meeting at a very small angle. 



Dimensions of the closed shell : — Length 9 lines, width 10 lines, 

 and depth 6 lines. 



There are two specimens from Dundry in the Bristol Museum, 

 and one in the British Museum, from Les Moutiers, Erance ; but I 

 have been unable to identify it with any described form. 



Opis spathttlostjs, n. sp. Plate XVIII. figs. 20, 20 a. 



Shell flattened, very slightly convex, not oblique. Umbo exceed- 

 ingly prominent and produced, central, flattened, bending gently 

 forward, but comparatively erect ; its apex being subacute, slightly 

 curving inward, but distant. Lunule extremely deep and hollow, 

 with well-developed flattened sides and defined subangular edges, 

 the surface in front of the umbo turning rapidly round and 

 doubling almost upon itself to form it. The anterior side much 

 produced. The line of contour starting from the apex, being, for 

 nearly half the length of the shell, concave (round the edge of the 



