28 AMERICAN MARINE CONCHOLOGY. 
more or less tumid; columella smooth, inner lip expanded; outer lip 
usually thin, smooth internally. Operculum lamellar, nucleus external. 
Buccinum, Linn. 
Shell ovate, small, few-whorled ; aperture moderate ; columellar lip callous, 
expanded, forming a tooth-like projection near the anterior canal. Oper- 
culum ovate, nucleus apical. Nassa, Lam. 
Shell striated, imbricated, or tuberculated ; spire short; aperture large, 
with a slight oblique channel in front; inner lip much worn and flat- 
tened. Operculum lamellar, nucleus external. PurRpPuRA, Lam. 
Shell very small, limpet like; with a large aperture, channelled in front, 
and a minute lateral spire. No operculum. PEDICULARIA, Swains. 
Shell oblong, small, thick, with a long, narrow aperture; outer lip thick- 
ened, especially in the middle, dentated ; inner lip crenulated. Opercu- 
lum very small, lamellar. CoLUMBELLA, Lam. 
Shell obconic, ventricose, with irregular varices; spire short ; aperture long 
and narrow ; outer lip reflected, denticulated ; inner lip spread over the 
body-whorl ; canal sharply recurved, producing a varix on the back of 
the shell. Operculum small, elongated; nucleus in the middle of the 
straight inner edge. Cassis, LA. 
Shell oval, ventricose, dhin, spirally furrowed, without varices; spire small ; 
aperture very large; outer lip crenated. No operculum. 
Douium, Lam. 
Shell long turreted, dextral, many-whorled, granulated ; aperture subro- 
tund ; inner lip broadly reflected ; outer lip acute, arcuated and produced 
anteriorly ; aperture anteriorly sinuated; canal short. Operculum cor- 
neus, concentric ; apex terminal. CERITHIOPSIS, Forbes & Hanley. 
Shell long pointed, many-whorled ; aperture small ; canal short. Oper- 
culum pointed, nucleus apical. ; Acus, Humphrey. 
Shell cylindrical, polished ; spire very short, suture channelled; aperture 
long, narrow, notched in front; columella callous, striated obliquely ; 
body-whorl] furrowed near the base. No operculum. 
Outrva, Lam. 
Genus BUCCINUM, Linneus. 
Syst. Nat., edit. x. 734. 1758. 
Tritontum, O.’Fabricius (not Link), Faun. Green. 395. 1780. 
Shell ovate or oblong, covered by a horny epidermis; spire 
elevated, apex acute; aperture large, oval, emarginate in front ; 
canal wide, truncated, dorsally more or less tumid; columella 
smooth; inner lip expanded; outer lip usually thin, smooth in- 
ternally. 
Animal with eyes on slight eminences at the outer bases of the 
tentacles. 
The genus contains few species, of Arctic distribution. 
