340 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Juiie 15, 



posterior border rounded ; radiating costse very numerous (about 60 

 or 70), rounded, with conformable densely striated insterstitial spaces. 



The costes are elevated, but very narrow and almost thread-like ; 

 the intervening spaces are transversely striated and are wider than 

 the costae ; the height and opposite diameter are nearly equal. 



In Gloucestershire this shell occurs in the middle division of the 

 inferior oolite ; its convexity and round elevated costse, and the smaller 

 height of the shell, will serve to distinguish it from L. punctata, 

 which occurs with it in the Cotteswolds. 



Locality. — Ponton, Lincolnshire. 



Ceromya siMiLis, Lycett. Pl. XIV. fig. 2. 



Testa ovato-oblonga, convexa ; umbonibus magnis anticis cm'vatis ; latere 

 antico brevi convexo, postico elongato mediocriter attenuate ; basi cur- 

 vato ; striis concentricis magnis regularibus et crebris. 



Shell ovately oblong, convex ; umbones prominent, anterior, and 

 curved forwards ; anterior side convex, short, its margin rounded ; 

 posterior side elongated, the superior border nearly horizontal, the 

 shell becoming attenuated towards the posterior border ; the lunula 

 is excavated, the base curved ; the sides of the valves have regular 

 strongly impressed and closely arranged concentric striations. 



The form of this species presents a near approximation to Ceromya 

 concentrica, except that it is more elongated and oblique, the um- 

 bones more especially being more produced and having a much 

 greater anterior curvature ; the sides of the shell are also much more 

 deeply marked by the striations than in C. concentrica. The form 

 is really intermediate between that shell and C. excentrica, being less 

 elongated than the latter species. 



Height 1 5 lines ; length 22 lines ; diameter through both the valves 

 14 lines. 



Locality. — Ponton, in the shelly beds ; also in the lower strata of 

 Stamford, Morcot, &c. 



Cyprina nuciformis, Lycett. Pl. XIV. fig. 3. 



Testa subnuciformi, convexa; umbonibus magnis curvatis; marginibus 

 rotundis ; latere postico angulo obtuse obliquo ; lunula excavata. 



Shell subcordiform or nut-shaped, convex ; umbones large, pro- 

 minent and curved forwards ; margins of the valves rounded ; pos- 

 terior side with an oblique obtuse angle ; lunule large, slightly ex- 

 cavated. 



This species is distinguished from Venus trapeziformis, Roemer, 

 by the greater prominence of the umbones, by their less obliquity, 

 and by the more globose figure of the shell : a Great Oolite 

 Minchinhampton species is distinguished from it by a more com- 

 pressed form and small umbones. In the Cotteswolds it occurs in 

 the middle portion of the inferior oolite, where it is not uncommon : 

 the height and length are about equal ; the convexity of the valves 

 is one-third less. 



Locality. — Ponton, Lincolnshire. 



