62 PALEONTOLOGY OF NEW JERSEY. 



moderately inflated and marked by from twenty-five to thirty strong, radiat- 

 ing plications, which are simple, rounded on the top, and separated by 

 rounded spaces of equal widtli^ and crossed by fine concentric lines of 

 growth, which arch backwards in crossing them. Stronger concentric 

 varices of growth also form a common feature of the shell. The hinge- 

 line is straight and equal in length to about one-third the length of the 

 shell from beak to base. Auriculations small and subequal; beak moderately 

 curved and central to the hinge-line; area moderately high, with a very 

 large central pit and the hinge destitute of teeth or other markings. Ante- 

 rior or straight side not at all gaping. 



As cited above, this species was originally described by Morton as a 

 Plagiostoma, but owing to the great multiplication of genera has been 

 referred to a difi"erent genus by every writer who has treated upon it. The 

 shell as seen in the single valve figured on Plate IX, fig. 4, would fall 

 between the genera Radula and Ctenoides, according to the characteristics 

 of these genera as defined by Stoliczka, with a leaning toward the latter of 

 the two, as the shell may be said to be absolutely straight on the anterior 

 margin; and, so far as can be proved by the specimen and from several 

 casts, must have been nearly, if not quite, without any gape of the valves. 

 The two genera, however, are, as there defined, so nearly alike that they 

 would seem hardly to afford specific differences so far as form, without sui'- 

 face markings and color, are concerned. 



Formation and locality. — In the Lower Green Marls of the Cretaceous at' 

 Holmdel and Freehold, New Jersey. 



Radula acutilineata. 



Plate IX, Figs. G and 7. 



Ctenoides acutilineata Conrad. J. A. N. S., PLila., 2d ser., Vol. Ill, p. SL'O, PI. XXXIV, 



Fig. 2. Gabb, Syuop., p. 114. 

 Lima acutilineata (Con.) Meek. Cbeck-list, p. 7. 

 Radula acutilineata (Conrad) Meek. Geol. Eept. N. J., 1868, p. 724. 



Shell small, obliquely ovate, and very ventricose; hinge-line very 

 short, with small acute auriculations, especially the anterior one, which is 

 pointed at the extremity. Anterior side of the shell rounded and full; 

 posterior side straightened above and rounded below. Surface of the 



