■ MO'LLUSCA. 543 



sions large and strong, o^f about equal size; pallial line parallel 

 with the truncated posterior margin for a short distance below 

 the posterior muscular impression, then bending abruptly for- 

 ward and continuing subparallel with the shell margin. 



Remarks. — This species occurs abundantly in the Marshall- 

 town clay-marl near Swedesboro, where it is preserved with the 

 shell in perfect condition. These specimens differ somewhat 

 from the original illustration of the species, but they have been 

 compared with authentic examples in the National IVCuseum, 

 from the type locality at Snow Hill, North Carolina, and they 

 seem to be specifically the same. Among the Show Hill Material 

 studied there are two somewhat different forms one of which is 

 essentially identical with the Swedesboro specimens, while the 

 other is a smoother shell in \yhich the strong concentric growth 

 lines are absent and in which the basal margin is convecx through- 

 out. Conrad's figure of the type specimen is nearly intermediate 

 in its characters between these two forms, but all should doubt- 

 less be included in one species. The Swedesboro examples 

 differ chiefly from the North Carolina ones in exhibiting a less 

 wide range of individual variation. The species differs from 

 B. trapezoidea in being somewhat more elongate, with the pos- 

 terior, obliquely truncate margin shorter, so that the postero- 

 basal extremity is lower down. 



Pormaiion and locality. — Marshalltown clay-marl, near 

 Swedesboro (177)- 



Geographic distribtttion. — New Jersey, North Carolina. 



Etea trapezoidea (Conrad). 



Plate LVIir., Figs. 20-21. Plate LIX., Pig. 7. 



i860. Vewilia trapezoidea Con., Jour. Acad. Nat. Sci. Phil., 2nd 



ser., vol. 4, p. 282, pi. 47, fig. 7. 

 i860. Crassatella Monmouthensis Gabb, Jour. Acad. Nat. Sci. 



Phil., 2nd ser., vol. 4, p. 302, pi. 48, fig. 19. 

 1 861. Crassatella Monmouthensis Gabb, Synop. Moll. Cret. 



Form., p. 168 (112). 

 1861. Venilia trapezoidea Gabb, Synop. Moll. Cret. Form., p. 



234 (178). 



