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( 2 ) Marine shells. 
Nerita. — Shell solid, semi-globular, flattened beneath, not umbilicated : aperture entire, 
semi-circular, the left margin flat, septiform, acute, often toothed ; teeth or crenu- 
lations on the inner surface of the right lip. Operculum with a projecting tooth. 
Plate XVI. Fig. 1. N. peloronta. (Idem. — Linn.) 
Natica. — Shell subglobular, umbilicated : aperture entire, semi-circular; left lip oblique, 
not toothed, callous ; the callosity modifying the umbilicus, and sometimes cover- 
ing it; right lip acute, always smooth inside. An operculum. 
Plate XVI. Fig. 2. N. vitellus. (Nerita vitellus. — Linn.) 
JANTHINEA. 
Janthina. — Shell ventricose, conoidal, thin, transparent: aperture triangular; columel- 
la straight, passing beyond the base of the right lip, which has a sinus in the mid- 
dle. No operculum. 
Plate XVI. Fig. 3. J. communis. (Helix janthina. — Linn.) 
MACROSTOMIANA 4 Genera. 
Shell ear-shaped, the aperture much dilated, the margins disunited, no columella, no operculum. 
Sigaretus. — Shell sub-auriform, nearly orbicular ; the left lip short and spiral: aperture 
entire, much dilated, rounded-oblong; the margins not united. 
Plate XVI. Fig. 4. S. concavus. 
Stomatella. — Shell orbicular or oblong, ear-shaped, imperforate: aperture entire, large, 
sub-longitudinal; right lip effuse, dilated, open. 
Plate XVI. Fig. 5. S. imbricata. 
Stomatia. — Shell ear-shaped, imperforate, spire prominent: aperture entire, large, ob- 
long; right margin and columella equally raised ; a transverse and tuberculated 
rib on the back. 
Plate XVI. Fig. 6, 6 ( a ). S. phymotis. (H. imperforata. — Chem.) 
Haliotis. — Shell ear-shaped, mostly flattened ; the spire very short, sometimes depress- 
ed, nearly lateral: aperture very large, ovate-oblong, and entire in perfect shells ; 
disk pierced with holes disposed in a line parallel to, and near the left margin, 
the last commencing with a notch. 
Plate XVI. Fig. 7- H. asinina. (Idem.— Linn.) 
PLICACEA 2 Genera. 
Aperture of the shell not effuse ; columella plaited. 
Tornatella. — Shell convolute, ovate-cylindrical, mostly striated transversely ; no epi- 
dermis : aperture oblong, entire, the right lip sharp ; one or more plaits on the 
columella. 
Plate XVI. Fig. 8. T. fasciata. (Voluta tornatilis.— Linn.) 
