MARINE MOLLUSCA OF THE UNITED STATES. te 
Shell minute, orbicular, depressed, few-whorled ; peristome continuous, 
entire, round ; operculum paucispiral. SEENEA, Fleming. 
Shell minute, discoidal, convex above, concave beneath, umbilicated ; sur- 
face glossy ; operculum thin, flexible, pellucid. 
CocHLIOLEPIS, Stimpson. 
Genus LITTORINA, Ferussac. 
The periwinkles are found on the sea-shore in all parts of the 
world; they can exist for a lengthened period out of water, and 
usually inhabit situations which are only covered by the sea at 
high tide. The species are numerous, and the genus is represented 
in all parts of the world. 
1. L. DILATATA, d’Orbigny. Fig. 144. 
Moll. Cuba, 207, t. 14, f. 20-23. 
Shell subpyramidally conical, rather thick, imperforated, livid- 
gray, encircled with white nodules; whorls slanting at the upper 
part; columella broadly concavely dilated, purplish-brown. 
Chiefly remarkable for the broadly excavated purple-brown 
columella, and conspicuous white nodules upon a livid-gray ground. 
Beaufort, North Carolina to West Indies. 
2. L. RupIs, Donovan. Fig. 145. 
(Turbo.) Brit. Shells, i. t. 33, f. 3. 1800. 
T. obligatus, Say, Journ. Philad. Acad., ii. 241. 1822. 
Shell very strong and coarse, subovate, ventricose ; whorls five 
to six, convex, tapering rapidly to a little elevated spire, and 
covered with revolving elevated lines and grooves; body-whorl 
with ten to twelve revolving costz, the intervening spaces finely 
reticulated ; lip plaited by the termination of the cost; about 
four of these on the next whorl, and obsolete above; base of the 
lip broadly bevelled; pillar-margin also broadly flattened; aper- 
ture regularly oval; color obscurely brownish, sometimes orange 
or olive, occasionally banded with white. 
Length 12.5 mill. 
New England and Middle States (N. Europe). 
3. L. TENEBROSA, Montagu. Fig. 146. 
(Turbo.) Test. Brit., 303, t. 20, f. 4. 1803. 
T. vestitus, Say, Journ. Philad. Acad., ii. 241. 1822. 
L. rudis (part), Stimpson, Shells N. E., 38. 1851. 
Shell small, conic, not as stout as rudis; spire elevated and 
pointed, as long as the aperture; whorls five to six, rounded, with 
