JTJKES-BROWNE : CRETACEOUS AND EOCENE VENERIDiE. 165 



Sunettina. I propose, therefore, to distinguish these Eocene shells 

 by the name of Meroena, and consider that they should rank as 

 a subgenus. In reality, of course, they are ancestors of our modern 

 assemblage of species known as Smieita, and they represent a stage in 

 its evolution from a more generalized form. 



The name Meroena is derived from Schumacher's name for the 

 genus (Meroe), and as type I take the first on M. Cossmann's list 

 (S. trigonula, Desh., see Fig. 2), which is a common shell in our 

 Barton Beds, as well as in the equivalent deposits of the Paris Basin, 

 The other two species are M. semisulcata, Lam., and M. polita, Lam., 

 with which M. Cossmann unites Cyth. separata, Desh. Another 

 species, has, however, been recently described by him, which forms an 

 interesting link between Meroena and typical Sunetta, for in shape, 

 dentition, and sharpness of the dorsal angle it comes near to some 

 recent forms, but has the smooth inner margins of Meroena. This 

 species is S. Caillaudi from the Middle Eocene of Bois Gouet (Loire 

 Inferieure). 



12. CrpRiMERiA, Conrad, 1864. 



This genus was founded on a right valve of the American Cretaceous 

 shell previously known as Cytherea excavata, Morton, and was 

 described ' as having (in that valve) a bifid oblique posterior cardinal 

 and two oblique anterior teeth, ' ' with an intermediate pit for the 

 reception of the tooth in the opposite valve." By this, Conrad 

 evidently meant that between the posterior and median teeth there 

 is a wide space into which a broad left median tooth would fit. 



As the generic characters of Cyprimeria are not correctlv given 

 either in Fischer's "Manuel de Conchyliologie " or in Eastman's 

 edition of Zittel's Palaeontology, Conrad's description of the right 

 valve may be supplemented by the following : — The left valve has 

 three separate and divergent teeth, the median being thick, triangular, 

 and bifid, the others narrow and entire. There are no lateral teeth, 

 and the anterior cardinal is parallel to the lunular border. The 

 pallial line is only slightly indented below the posterior muscular scar. 

 In shape the shell is orbicular and compressed. 



The genus Cyprimeria is supposed to be essentially Cretaceous, and 

 since species have been found in France, Germany, Bohemia, India, 

 and North America, it is rather surprising that none have yet been 

 discovered in British Cretaceous rocks. But, although the genus has 

 only yet been recognized in deposits of Cretaceous age, there is, of 

 course, no reason why it should not have survived into Eocene time, 

 and in the Eocene of the Paris Basin there is a shell described by 

 Lamarck as Venus oUiqua, which seems to be referable to Cyprimeria, 

 notwithstanding its small size. 



V. ohliqua has recently been well figured by M. Cossmann in his 

 " Iconographie Complete des Fossiles Eoceniques des Environs de Paris" 

 (1906), pi. ix, fig. 485 (three views), the interiors of both valves 

 being shown. From these figures it can be seen that the hinge-teeth 



1 Proc. Acad. Nat. Sci. Philadelphia, 1864, ^. 212. 



