56 AMERICAN MARINE CONCHOLOGY. 



i 



Genus VOLVA, Bolten. 



Museum. 1798. 

 1. Y. UNIPLICATA, Sowerby. Fig. 93. 



(Ovulum.) Proc. Zool. Soc., 135. 1848. 



Shell narrowty 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. 



ORDER I. PROSOBRANCHIATA. 



Section B. HOLOSTOMATA. 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 turbimform. 

 Family I. NATIGIDJE. Shell globular, few-whorled ; spire .small, 

 obtuse ; aperture semilunar ; lip acute ; pillar often callous. 



II. Shell elongated. 



Family II. PYRAMIDELLID^E. Shell spiral, turreted; nucleus 

 minute, sinistral ; aperture small ; columella sometimes with one 

 or more prominent plaits ; operculum horny, imbricated ; nucleus 

 internal. 



Family III. CERITHLAJLE. Shell spiral, elongated, man y-whorled, 

 frequently varicose ; lip generally expanded in the adult ; opercu- 

 lum horny and spiral. 



Family V. TURRITELLID^E. Shell tubular or spiral, upper part 

 partitioned off; aperture simple; operculum horny, many whorled. 



Family VI. LITTORINID^E. Shell spiral, turbinated, or depressed, 

 never pearly ; aperture rounded ; peristome entire ; operculum 

 horny, pauci-spiral. 



Family IX. TURBINID^B. Shell spiral, turbinated, or pyramidal, 



