MARINE MOLLUSCA OP THE UNITED STATES. 47 



Shell ovate, fusiform, small ; surface dull, smooth or longitudinally ribbed ; 

 epire elevated, shorter than the body-whorl ; columella flattened ; canal 

 short; outer lip with a small sinus at its jimction with the body-whorl. 

 (This genus may be known by its flattened columella.) Operculum as 

 in Pleurotoma (Boreal). Bela, Leach. 



Shell turreted, apical whorls nearly smooth, the others ribbed. Posterior 

 sinus of lip very large. No operculum. Animal without eyes. 



Plkurotomella, Verrill. 



Shell solid, subfusiform, smooth or longitudinally ribbed ; aperture linear, 

 tcith scarcely any canal in front ; columella smooth, simple; outer lip 

 acute, with a slight sinus posteriorly, near the suture. No operculum. 

 (Tropical.) Mangelia, Leach. 



Genus PLEUROTOMA, Lamarck. 

 Prodromus. 1799. 



1. P. BiCARiNATA, Coiithouy. Fig. 77. 



Bost. Journ. Nat. Hist., ii. 104, t. 1, f. 11, 1838. 



Shell minute, tapering at both extremities, turreted ; whorls six, 

 convex, with numerous revolving ribs and smaller ones inter- 

 vening ; about the middle a deep groove, with a prominent re- 

 volving rib on each side; sutures clearly defined. Aperture nar- 

 row, elliptical, ending in a short canal slightly inclining to the 

 left ; lip thin, toothed by the revolving ribs, with a slight notch 

 above ; pillar-lip arched at its upper third. Whitish, slate-color 

 or dusky-brown. 



Length 7.5, diam. 3.75 mill. 



2. P. BRUNNEA, Perkins. Fig. 78. 



Bost. Proc. 121. 18G9. 

 P. j-)licata, Adams (not Lamarck), Bost. Journ. Nat. Hist., iii. 318, t. 3, f. 6. 



1840. 

 P. dech'vts, Loven, 1846. (JeflFreys.) 



Shell minute, thick, fusiform ; whorls six, convex ; body-whorl 

 with about twelve prominent oblique folds, crossed by ten or more 

 revolving threads, rendering the folds somewhat nodulous ; suture 

 deeply impressed; whoi'ls above with folds and revolving lines; 

 spire pointed, somewhat turreted. Aperture narrow, less than 

 half the length of the shell ; lip arched, thickened by one of the 

 folds; notch above deep, distinct and smooth. Canal short. Epi- 

 dermis ashen-brown ; beneath this, white; lip brownish within. 



Length 6, diam. 3 mill. 



Massachusetts, Conntctictit, New York {rare). 



Massachusetts (rare), Eur. 



