NAVICELLA. NERITINA. 49 
LES NERITACES. 
NAVICELLA. FLUVIATILE. 
Elliptical or oblong, concave beneath ; spire erect ; 
margin always inflected; outer lip flattened, 
acute, angulated, and destitute of teeth; aper- 
ture provided with a solid flat operculum, 
having a lateral point. 
N. ExvuipricaA. Smooth, shining, spotted 
and streaked with blue, purple, or brown, covered 
with an olivaceous epidermis ; spire curved, promi- 
nent, extending beyond the margin; diam. 3. 
W. 37. 9. 
NERITINA. FLUVIATILE. 
Thin, semi-globose or ovate, flattened below ; with- 
out an umbilicus ; aperture semi-circular ; imner 
lip flattened, and reflected on the columella, 
sometimes slightly crenated ; outer lip destitute 
of teeth, or crenulations on its internal face ; 
aperture provided with an operculum, having a 
lateral point. 
N.zEBRA. Oblong-globose, glabrous, fulvous 
red, with longitudinal flexuous very oblique black 
lines ; aperture white; lip denticulated; diam. ?. 
W. 35. 18. 
N. corona. Oblong-globose, striolate, black; 
D 
