230 CRETACEOUS LAMELLIBRANCHIA. 



margin rounded. Ventral margin straight or slightly convex. Posterior margin 

 truncated, sliglitl}- convex. Postero-dorsal margin slightly concave, nearly parallel 

 to the ventral margin. Umbones broad, curved inwards and backwards. The 

 part of the shell in front of the umbones is slightly depressed; the part behind the 

 umbones is more deeply depressed. Surface with well-marked growth-rings. 

 Length 87 mm. ; height 59 mm. 



Aj)i)iifies. — In this species the sides of the shell are more flattened, the autero- 

 dorsal margin is more convex, and the part of the shell in front of the umbones is 

 less depressed than in P. ocdlis. The hinge has not been seen, but the form of the 

 shell agrees closely with that of ty})ical species of Panopea. 



Fig. 28. — Panopea, sp. Lower Greeiisand (' .-^capniti's J.rtls), Whale Chine, Atherfield. Sed-jwick 

 Museum. Internal cast of right valve. Natural size. 



Jt'riitarkt^. — In addition to the specimen figured, which was collected by 

 C. J. A. Meyer, an internal cast and the posterior part of a left valve only have 

 been seen. 



Distribution. — Upper Greensand (zone of ScliUviilntchid rarinna) of Blackdown. 



P.\xnpj;,\, sp. Text-fig. 28. 



Internal casts resembling /'. ^Li'ijcri, but with the po.■^terior border obliquely 

 truncated, occur in the Lower Greensand (" Scaphites " Beds) of "Whale Chine, 

 Atherfield. 



