MARINE MOLLUSCA OF THE UNITED STATES. 87 
Family TURBINIDA. 
Shell spiral, turbinated or pyramidal, nacreous inside. Oper- 
culum calcareous and paucispiral, or horny and multispiral. 
Animal with a short muzzle; eyes pedunculated at the outer 
bases of the long and slender tentacles; head and sides orna- 
mented with fringed lobes and tentacular filaments. 
Distribution universal; feeding on sea-weeds. 
The shells are brilliantly pearly under the epidermis and within 
the aperture. 
Synopsis of Genera. 
Shell turbinated, solid; whorls convex, often grooved or tuberculated ; 
aperture large, rounded, slightly produced in front ; operculum shelly and 
solid, callous outside, and smooth, or variously grooved and mammillated, 
internally horny and paucispiral. Touro, Linneus. 
Shell thin, globosely depressed, whorls convex, smooth or transversely 
striated ; aperture nearly circular ; columella ending in a simple point. 
MarcGarita, Leach. 
Shell minute, not nacreous, depressed, few whorled, deeply umbilicated ; 
peristome entire, nearly continuous, sinuated on its inner side, and 
slightly so externally ; operculum shelly, multispiral. 
ADEORBIS, 8. Wood. 
Genus TURBO, Linneus. 
Syst. Nat. Edit., x. 761. 1758. 
1. T. cRENULATUS, Gmelen. Fig. 168. 
Syst. Nat., 3575. 1790. 
Shell ovate, imperforated, sutures of the spire excavated, whorls 
covered with papillose nodules, convex or slightly angulated in 
the middle, and ridged, ridges generally squamose, the upper 
scales being more prominent and erect; operculum thick, testa- 
ceous. 
Whitish, with rays or blotches of fawn-color or reddish, pearly 
within. 
North Carolina to West Indies. 
Genus MARGARITA, Leach. 
Journ. de Phys., lxxxviii., 464. 1819. 
The species of this genus are principally inhabitants of north- 
ern or antarctic seas. They are generally more depressed, 
smoother, and smaller than Z'urbo, which is tropical in distribu- 
tion. 
