GASTEROPODA OP THE LOWER GREEN MARLS. 51 



This species is somewhat similar to P. Newberryi M. & H., from the 

 upper Missouri region, but is more equally biconical, less ventricose in the 

 middle in proportion to the length, and has the longitudinal ribs more dis- 

 tant. I know of no other species with which it may be readily confounded. 



Formation and locality: The specimen figured, representing the surface 

 structure, is from a matrix in an iron sand nodule, found in di-ift clay, at 

 Cliffwood, New Jersey, and is in the collection at Columbia College. The 

 figure is made from a gutta-percha impression in this natural mold. These 

 nodules are supposed to come from the Lower Marls, as the fossils are all 

 from that horizon. 



Pyriftjstjs cunbus, n. sp. 

 Plate IV, Figs. 9-11. 



Shell of medium size, short-fusiform, nearly twice as long below as 

 above the periphery of the last volution when viewed from in front, and 

 almost regularly sloping from that point to the pointed anterior extremity, 

 as seen in the cast; apical angle about 50° or 55° ; volutions about 

 four; subangular on the periphery and marked by moderately distant but 

 distinct vertical folds, which are obsolete on the lower third of the volution, 

 but increase in strength and distance with the increased growth of the. shell. 

 Twelve of these folds can be counted on the body whorl of the best pre- 

 served cast. Umbilical cavity in the cast, as left by the removal of the colu- 

 mella, large and destitute of markings or folds of any kind; aperture 

 cuneate-elliptical, sharply pointed beloAV and angular above ; surface char- 

 acters of the shell unknown. 



This species is of about the size of P. erraticus, biit differs somewhat 

 in the form of the volutions and in the less elevation of the spire. The 

 volutions are more angular on the periphery and the angulation is com- 

 paratively higher than in that species, while the vertical folds are more 

 closely arranged. The lower portion of the volution is also not constricted 

 between the body of the volution and the anterior beak, so that the shell is 

 of a wedge-shaped form below the periphery. It somewhat closely resembles 

 P. Newberryi M. & H.^ 



> U. S. Geol, Sury. Terr., vol. 9, Invert. Pal., p. 346, PI. xxxi, Fig. «, a-d. 



