GASTEEOPODA OP THE LOWER aEBEN MARLS. 59 



Genus Trachytriton Meek. 



Trachytriton atlanticum, n. 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 Bostellaria 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. 



