MARINE MOLLUSCA OF THE UNITED STATES. 47 
Shell ovate, fusiform, small; surface dull, smooth or longitudinally ribbed ; 
spire elevated, shorter than the body-whorl; columella flattened ; canal 
short; outer lip with a small sinus at its junction with the body-whorl. 
(This genus may be known by its flattened columella.) Operculum as 
in Plewrotoma (Boreal). Bea, Leach. 
Shell turreted, apical whorls nearly smooth, the others ribbed. Posterior 
sinus of lip very large. No operculum. Animal without eyes. 
x PLEUROTOMELLA, Verrill. 
Shell solid, subfusiform, smooth or longitudinally ribbed; aperture linear, 
with scarcely any canal in front; columella smooth, simple; outer lip 
acute, with a slight sinus posteriorly, near the suture. No operculum. 
(Tropical. ) ManeGeuia, Leach. 
Genus PLEUROTOMA, Lamarck. 
Prodromus. 1799. 
1. P. BICARINATA, Couthouy. Fig. 77. 
Bost. Journ. Nat. Hist., 11. 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. 
Massachusetts (rare), Hur. 
2. P. BRUNNEA, Perkins. Fig. 78. 
Bost. Proc. 121. 1869. 
P. plicata, Adams (not Lamarck), Bost.Journ. Nat. Hist., iii. 318, t. 3, f. 6. 
1840. 
P. declivis, Lovén, 1846. (Jeffreys. ) 
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; whorls 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, Connecticut, New York (rare). 
