GASTEROPODA FROM BASE OF THE UPPER GREEN MARLS. 189 
BULLIDA. 
Genus BULLA Lamarck. 
BULLA CONICA, 0. sp. 
Plate xx, Figs. 12, 13. 
Shell of medium size, ovate in general outline, smallest above and regu- 
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 Green Marls, at Shark River, New Jersey. Collection at Columbia 
College. Collected by Dr. Britton. 
