204 MOLLUSCA FROM THE CRAG. 



when the specimens can be compared ; there are, however, some differences in the 

 descriptions : it is therefore thought best to retain its present name. As this latter 

 species appears its nearest relative, it may be only necessary to point out what are the 

 distinctions, relying upon the description by that author, who, in comparing his shell 

 with the geographica, seems to think a specific character exists in being less equilateral, 

 and in the straight dorsal line of nitens, with a more convex ventral margin. Our 

 shell, on the contrary, appears to have its dorsal margin more rounded than that of 

 geographica, and much resembles in outline the virginea, but the smooth and glossy 

 exterior differs from all that I have seen, with the exception of nitens ; the dental 

 characters appear the same, the central one bifid in the left valve, with two sub-bifid 

 in the right ; but the palleal scar, according to the figure, goes deeper into his shell 

 than it does into our Crag fossil. 



4. TAPES TEXTURATA? Lamarck. Tab. XX, fig. 3 a c. 



VENUS TEXTURATA. Lam. Hist, des An. sans Vert., 2d ed., p. 355, No. 43. 

 TAPES TEXTUKATA. G. Sowerby. Thesaur. Conch. Tapes, No. 39. 



Spec. Char. Testa tenui, cordato-ovatd, compressiusculd, incequilaterali ; transversim 

 striatd, striis numerosis, confertis. 



Shell thin, ovately heartshaped, somewhat compressed, inequilateral ; transversely 

 striated, striae numerous, close set. 



Length, \\ inch. 



Locality. Red Crag, Walton-on-the Naze. 



The specimen figured is the right valve with three teeth diverging from imme- 

 diately beneath the umbo. The lines which cover the exterior are generally parallel 

 to the margin of the shell, but they occasionally anastomose, or run into each other 

 like those upon the recent species, T. texturata. There is, however, a slight difference 

 in form from that shell, and thelunule is not so distinctly marked ; but having only one 

 specimen, and that imperfect, I am unwilling to do more than assign it provisionally to 

 what appears at least its nearest relative ; should, however, future examination of 

 better specimens justify a specific distinction, I would claim for the Crag fossil the 

 name of habilis. 



VENERUPIS.* Lamarck, 1818. 



VENUS (sp.) Linn. 



DONAX (sp.) Id. 



CUNEUS (sp.) Dacosta. 



IRUS. Oken, 1815. 



PETRICOLA (sp.) Turt., 1822. 



PETRIJFORA. Latr., 1827. 



VENERIRUPIS. Blainv., 1825, G. Sow., 1839. 



VENERUPES. Swains., 1840. 



* Etym., Venus, and rupis, a rock. 



