56 AMERICAN MARINE CONCHOLOGY. 
Genus VOLVA, Bolten. 
Museum. 1798. 
1. V. uNIPLICATA, Sowerby. Fig. 93. 
(Ovulum.) Proc. Zool. Soc., 185. 1848. 
Shell narrowly oblong, rather thin, whitish or orange-rose, ex- 
tremities rather produced, blunt, back transversely minutely stri- 
ated; lip moderately thickened, flexuous, widely sinuated at the 
lower part; columella plicate above. 
South Carolina, southwards. 
OrvER I. PROSOBRANCHIATA. 
Section B. Hotostomata. Sea-snails. 
Shell spiral or limpet-shaped; rarely tubular or multivalve ; 
margin of the aperture generally entire; operculum horny or 
shelly, usually spiral. Animal with a short non-retractile muzzle; 
respiratory siphon wanting, or formed by a lobe developed from 
the neck; gills pectinated or plume-like, placed obliquely across 
the back, or attached to the right side of the neck; neck and sides 
frequently ornamented with lappets and tentacular filaments. 
Mostly phytophagous. Aperture channelled in front, with a less 
distinct posterior canal. 
I. Aperture entire. Shell globular or turbiniform. 
Family I. Naticipm. Shell globular, few-whorled ; spire small, 
obtuse ; aperture semilunar; lip acute; pillar often callous. 
II. Shell elongated. 
Family II. PyrammpEniipm. Shell spiral, turreted; nucleus 
minute, sinistral; aperture small; columella sometimes with one 
or more prominent plaits; operculum horny, imbricated; nucleus 
internal. 
Family III. Cerirarap#. Shell spiral, elongated, many-whorled, 
frequently varicose; lip generally expanded in the adult; opercu- 
lum horny and spiral. 
Family V. TurrireLtip#. Shell tubular or spiral, upper part 
partitioned off; aperture simple; operculum horny, many whorled. 
Family VI. Lirrorinip#&. Shell spiral, turbinated, or depressed, 
never pearly; aperture rounded; peristome entire; operculum 
horny, pauci-spiral. : 
Family 1X. Tursinip@. Shell spiral, turbinated, or pyramidal, 
