GASTEROPODA FEOM BASE OF THE UPPER GREEN MARLS. 189 



BULLION. 



Genus BULLA Lamarck. 



Bulla conica, n. sp. 

 Plate xxiii, Figs. 12, 13. 



Shell of medium size, ovate in general outline, smallest above and regn- 

 larly expanding to below the middle, or for about two-thirds of the length 

 of the shell, giving' a somewhat conical aspect. Spire concealed, the upper 

 end of the shell appearing as subtruncate. Base of the shell more rapidly 

 contracted for the lower third. Aperture elongate, narrow above, widening 

 below and somewhat pointed at the base. Columellar lip somewhat twisted 

 in the lower part as shown on the cast, but destitute of any fold or tooth- 

 like ridge. Axis apparently imperforate. Surface, as shown by the cast, 

 marked by fine spiral or revolving depressed lines, and by obscure trans- 

 verse lines of growth crossing them. The revolving lines appear to have 

 been rather finer near the upper end of the shell, and on the basal slope of 

 the volution two or three of them are perceptibly more distant than those 

 immediately above them. 



This shell differs from B. Mortoni L. & F., from the lower beds, in its 

 more conical outline, the upper end being small and gradually expanding 

 to below the lower third of the length. The summit also is more broadly 

 truncate. 



Formation and locality: In Blackish Green Marls, at the base of the 

 Upper Grreen Marls, at Shark River, New Jersey. Collection at Columbia 

 College. Collected by Dr. Britton. 



