82 AMERICAN MARINE CONCHOLOGY. 
smooth, and covered with a rough, greenish-yellow epidermis; 
sutural region depressed and sub-channeled; the spire scarcely 
prominent above the very large lower whorl, and placed a little to 
one side; aperture oblique, semicircular. 
Length 5, diam. 6 mill. 
New England. 
Genus RISSOA, Frémenyille. 
Desmarest, Bull. d. Sc., parla Soc. philom., 7. 1814. 
Cingula, Fleming, Brit. Anim., 297, 305. 1828. 
The animal has large, slender tentacles, with eyes on small 
prominences near their outer bases; the foot is pointed behind; 
the operculigerous lobe has a wing-like process and a filament on 
each side. 
Universally distributed, but principally in the north temperate - 
zone. They range from high water to one hundred fathoms, but 
abound most in shallow water, near the shore, on beds of fucus 
and zostera. 
1. R. minuta, Totten. Fig. 153. 
(Turbo.) Amer. Journ. Science, xxvi. 369, f. 7. 1834. 
Shell minute, conic, thin, polished, elevated to an obtuse apex ; 
whorls five, convex, with very fine transverse strize; suture dis- 
tinct, with a round shoulder on the whorl; aperture oval, entire, 
rounded at the base, very slightly angular above; lip sharp; lower 
portion of the pillar-lip slightly recurved, with a loosely attached 
enamel which rises before an umbilical pit; operculum horny, sub- 
spiral; yellowish-brown, usually covered by a dark green pigment. 
Length 3.75, diam. 1.5 mill. 
Animal dusky-brown; tentacles, and a line on each side the 
neck, light drab. Very active in movement. 
New England. 
2. R. pation, Mighels and Adams. Fig. 154. 
(Cingula.) Bost. Journ. Nat. Hist., iv. 48, t. 4, f. 22. 1844. 
Shell minute, ovate-conic, smooth, pale horn-color; whorls more 
than four, convex; suture much impressed; last whorl broad, 
larger than the rest of the shell; aperture ovate-orbicular, left 
margin with a lamina. 
Length 2, diam. 1.25 mill. 
Maine. 
