166 PALEONTOLOGY OF NEW JERSEY. 



lower third of the shell's length, giving it a subcorneal or truncato-conical 

 outline, very readily distinguished in comparison with the form of this 

 species. 



Formation and locality : In the blackish green marls of the Lower Marl 

 Bed, at Crosswick's Creek, New Jersey; collection at Rutgers College, col- 

 lected by Dr. N. L. Britton; and also from the collection Acad. Nat. Sci., 

 Phila., but without any indications of locality other than " Cret. N. J." 



Class SCAPHOPODA. 



DENTALIID^. 



Genus DENTALIUM Linnseus. 



Dentalium subarcuatum. 



Plate XX, Figs 19-24. 



Dentalium subarcuatum Conrad: Jour. Acad. Nat. Sci., Phila., 2d ser., vol. 2, PL 

 XXIV, Fig. 13; Gabb, Synopsis, p. 49; Meek, Cteck List Cret. and Jur. 

 Foss.^ p. 17; Geol. N. J., Newark, 1868, p. 728. 



Shell small, and as seen in casts, the usual condition in which it is 

 found, slender and round, very gradually tapering and very genlly arcuate 

 throughout its length. A specimen 1 inch long measures only one line in 

 diameter at the larger end, and less than half that at the smaller end. Along 

 the dorsal hne of the cast there is a rounded elevated ridge, with a flat- 

 tened area on each side of it, traversing the entire length, and also in some 

 cases a depressed line a little distance from the ventral center on each side, 

 and more seldom other depressed longitudinal lines between these and the 

 dorsal line. On still other casts the dorsal line or ridge is only faintly 

 marked, and all others obsolete, leaving the cast comparatively smooth. 

 On a specimen which preserves the substance and shows the surface struc- 

 ture about the same proportions or rate of increase is shown, allowing for 

 its partially compressed condition. On the posterior two-thirds of the 

 length the surface is longitudinally lined with sharp distinct ridges, with 

 broad flattened interspaces. Seven of the ridges can be seen on one side of 

 the specimen, as it lies in the marl, indicating the existence of twelve or 



