138 



( !KETACEOUS LAMELLIBRANC111A. 



Description. — Shell large, oval, convex, moderately inequilateral, anterior part 

 produced. Antero- dorsal margin concave. Anterior margin rounded, passing 

 gradually into the convex ventral margin which curves upward to join the 

 posterior margin. Posterior margin rounded, sometimes forming a large and 

 rounded angle with the ventral margin, but sometimes passing into it gradually. 

 Postero-dorsal margin convex. Postero-dorsal part of valves compressed, some- 

 times limited by an indistinct carina. Umbones prominent, curving forward and 

 inward. Lunule indistinctly limited. Escutcheon narrow, deep, with a sharp 

 edge. Ornamentation consists of growth-lines. 



Fig. 2u. — Cyprina (Vcnilicaniia) protensa, sp. nov. Lower Greensand (Perna-bed), Atherfield. 

 Sedgwick Museum. Right valve, x 4-. 



Measui 



•ements 





(i) 



Length 



10G 



Height 



84 



(5) 



(6) 



75 



49 mm 



GO 



40 „ 



(2) (3) (1) 



. 105 . 103 . 99 



89 . 91 . 88 



(1 — 5) Pema-hed, Atherfield. 

 (0) Crackers, Atherfield. 



Affinities. — The characters which distinguish this species from G. angulata, 

 Sowerby, are : the umbones are less anterior and the shell is less inequilateral ; 

 the umbonal part of the shell is relatively smaller; the carina is less distinct; the 

 anterior part of the shell is more produced ; the posterior part is more rounded ; 

 the ventral margin has a greater curvature ; the shell is less inflated, so that the 

 marginal parts of the valves meet at a smaller angle. The anterior part of the 

 shell resembles that of G. I rim rata, but the posterior part is more rounded, and 



