31 
NERITA. 
Gen. Char. A subglobose univalve,, obliquely de- 
pressed beneath ; columella solids subtrans- 
verse, flattened, with a linear, sometimes 
toothed edge ; aperture semicircular, closed 
by an operculum. 
Both marine and fresh-water animals possess shells 
of this genus ; but those of the fresh-water hitherto known 
have no teeth upon the edge of the expanded columella. 
Neritae are generally strong shells with large apertures ; 
they have but few whorls, the last of which is commonly 
very large. The aperture is semicircular in consequence 
of its being half closed by the flattened columella, which 
forms the character of the genus. The recent species* 
and some even of the fossil ones, are ornamented with 
various colours, but they are seldom bright, and in gene- 
ral few, and disposed in small markings. 
NERITA laevigata, 
TAB. CCXYIL —Fig. 
Spec. Char. Pointed, smooth ; spire conical, with 
straight sides ; base convex. 
Remarkably smooth, shining; the aperture is much 
wider than long ; around the centre of the last whorl is a 
very obscure sulcus. 
From the inferior Oolite at Dundry, Mr. Miller’s col- 
lection. The specimens do not exhibit the columella. 
