DESCRIPTIONS OF SPECIES. 



MOLLUSC A. 



Class GASTEROPODA. 



Subclass PROSOBRANCHIATA. 



Order PECTINIBRANCHIATA. 



Family MURICID^. 



Genus TliDIOLA Bolton. 



TUDICLA PLANIMARGINATA, n. Sp. 



Plate I, Figs. 1-3. 



Shell small or somewhat below a medium size, very ventricose, with 

 a very low spire composed of but little more thau two entire volutions in 

 the cast; outer volution large, forming the great bulk of the shell and 

 having a diameter considerably greater than the entire height, includino- 

 the short beak and canal. Volutions marked on the periphery by a flat- 

 tened, vertical band, bordered above and below by an angulation; a second 

 angulation also marking the upper surface midway between the top of the 

 vertical flattening and the suture line, and still another on the under side of 

 the volution near the base of the beak; columellar cavity only of medium 

 size, with aperture large, wider or about as wide as high, but little modi- 

 fied on the inner side by the preceding volution; lip slightly expanded; 

 surface unknown. 



The species somewhat resembles in its general appearance Pyropsis 

 trivolvis Grabb, from the Middle Marls; but it has a much lower spire, com- 

 posed of fewer volutions, and the anterior beak has been quite short. 

 MON xvin 3 ;53 



