GASTEROPODA OF THE LOWER GREEN MARLS. 59 
Genus TRACHYTRITON Meek. 
TRACHYTRITON ATLANTICUM, 0. sp. 
Plate v, Figs. 8-11. 
Shell small, the casts seldom reaching a length of more than an inch 
and a quarter; spire with an apical angle of about 40° to 45°; volutions 
four and a half to five in number, rather convex and moderately distinct, 
the sutures in the cast being distinct and the spaces left by the removal of 
the shell quite considerable; last volution large, forming more than half the 
entire length, and being as long below the point of greatest diameter as the 
length of the spire above, giving an equally biconical or fusiform feature 
to the cast, with a moderately long and somewhat curved beak and canal; 
aperture large, pointed above and slightly extended below; narrow-elliptical 
in outline, with the outer margin rather more convex than the inner one; lip 
of the outer volution apparently slightly deflected; the surface of the volu- 
tions have been marked by revolving lines, at least in the lower part, as is 
shown by their remains on the surfaces between the volutions of the cast; 
and by proportionally strong, vertical folds, three of which in each volution 
have been stronger than the one or two intermediate ones, and have left 
their deeper impression both on the surface of the cast and on the imprint 
of the exterior, as seen between the whorls. 
The species is rather an abundant one at the one locality, and closely 
resembles, in the conditions of internal casts, those of Rostellaria curta, 
herein described, and with which it is associated; but it may be distinguished 
readily enough by a comparison of the prolongation of the anterior beak 
and the size of the cavity left by its removal, it being much longer, more 
slender, slightly twisted, and the cavity altogether smaller than in that one. 
The spire is also more slender, and the body volution does not contract so 
rapidly below the point of greatest diameter as in that species. 
Formation and locality: In the blackish green layers of the Lower Green 
Marls at Crosswicks Creek, near New Egypt, New Jersey. In the col- 
lection at Rutgers College. 
