54 TRACHELIPODA. PILEOLUS. 
umbilicate; spire short, sometimes very short, with the 
apex very rarely pointed ; aperture large, semi-circular, 
and but seldom effuse; outer lip sharp edged, smooth 
within ; columellar lip oblique, its edge nearly straight, 
destitute of teeth, generally thickened, and sometimes with 
a coating of enamel spread thickly over the umbilicus ; 
umbilicus usually large, having a spiral callosity within, 
which sometimes increases so as to cover it, and is some- 
times very small, in a few instances nearly obsolete, so 
much so as hardly to be perceptible ; operculum testaceous 
in some species, and horny in others. 
Natica epiglottina. Plate IV. fig. 39. = 
The species are numerous, and inhabit the ocean, the East and West Indies, 
Mediterranean, and British Coasts. 
There are also many fossil species, whose forms bear a remarkable simili- 
tude to the recent species, and even some of them retain their colours. They 
are chiefly met with in the newer formations over the chalk, more particularly 
in the Crag, London Clay, and Calcaire-grossier. 
Genus LXVI.— NERITA. — Lamarck. 
Generic Character.— Shell solid, generally thick, semi- 
globular, or obovate ; spire very short ; base of the body, 
for the most part, flattened beneath, but destitute of an 
umbilicus ; aperture semicircular ; outer lip sharp in the 
margin, and crenulated or toothed on the inner side ; inner 
lip generally flattened, sharp on the margin, which lies 
oblique to the axis of the shell, and, for the most part, 
dentated or crenated; a small prominence exists at the 
lower extremity of the inner lip, between which and the 
inner lip, the small appendage to the operculum slides, as 
the animal opens or closes the aperture for egress, moving 
in the same manner as a door on its hinges, when the ani- 
mal protrudes its body ; operculum testaceous. 
Nerita aperta. Plate V. fig. 6. Found in the London 
Clay at Barton, and Cowell Bay, Isle of Wight. 
The Neritz are distinguished from the Neretine by the thickness of their 
shell, the teeth on the margin of the pillar lip, and in being destitute of the 
thick horny epidermis which invests the Neritine ; and from Natica by the 
flattened area which is produced by the thickened columella. 
The Nerite are marine shells, and the species are pretty numerous, princi- 
pally inhabiting the seas of the tropics, and the warmer parts of Europe. 
Fossil species are met with in the London Clay, and contemporaneous for- 
mations of France and Italy. 
Genus LX VII. — PILEOLUS. — Cookson. 
Generic Character.— Shell concave ; spire internal, 
