58 AMERICAN MARINE CONCHOLOGY. 
spirally contorted into the umbilicus, the apex more or less dilated, con- 
vex, and rounded. Operculum large, horny, simple. Mamma, Klein. 
Shell ventricose, imperforate ; spire with the apex acute ; whorls smooth, 
without epidermis ; aperture very wide; inner lip with a large smooth 
callus covering part of the body-whorl and concealing the umbilicus. 
Buwsus, Bronn. 
Shell longitudinally oval, thin, smooth, white, not umbilicated, covered with 
a light-brown epidermis; spire elevated, suture canaliculated ; aperture 
oval, produced in front. Operculum pauci-spiral, horny, thin. 
AMAvUROPsIs, Morch. 
Shell oval, flattened, ear-shaped, striated ; spire minute, depressed ; aper- 
ture very wide, oblique ; umbilicus none ; inner lip curved posteriorly and 
spread thinly over the body-whorl. Operculum very small and rudi- 
mentary. Sicaretus, Lamarck. 
Shell thin, small, ear-shaped, pellucid, fragile ; spire very small; aperture 
large, patulous; inner lip receding. No operculum. 
MARSENINA, Gray. 
Shell thin, small, subglobose, composed of two rapidly enlarging volutions ; 
aperture large, subovate; lip thin, not joined behind; usually covered 
with a velvety epidermis. No operculum. VELUTINA, Blainyille. 
Genus NATICA, Adanson. 
Hist. Nat. Senégal, 172. 1757. 
1. N. Arrinis, Gmelin. Fig. 94. 
(Nerita.) Syst. Nat., 3675. 1790. 
NV. clausa, Brod. et Sowb. Zool. Journ., iv. 860. 1829. 
NV. consolidata, Couthouy, Bost. Journ. Nat. Hist., ii. 89, t.3, f. 14. 1838. 
Shell subglobose; whorls four or five, subconvex, partially 
flattened or even concave near the sutures; spire very short, ob- 
tuse; suture distinct; aperture oval, widest above; lip sharp, 
thickened, and rounded towards the umbilicus; callus depressed, 
enlarged at the upper angle, and in mature specimens quite con- 
cealing the umbilicus; epidermis thin, greenish-brown. Opercu- 
lum and throat milk-white. 
Length 12.5, diameter 14 mill. 
Obtained from stomachs of fishes. 
Cape Cod, Mass., northwards (Hur.). 
9. N. pusiLuA, Say. Fig. 95. 
Jour. Philada. Acad. Nat. Sciences, ii. 257. 1822. 
Shell thin, suboval, cinereous, or rufous, with sometimes one 
or two obsolete, dilated, revolving bands;.columella callous; 
eallus pressed laterally into the umbilicus, whitish; umbilicus 
