MOLLUSCA. 
407 
outer lip with two deep notches near its internal upper edge, 
and a bloody mark at the base of the inner teeth. One inch 
long. Inhabits the seas of South America. 
Genus 57.—NERITOIDES.— Brown. 
Generic Character. —Shell strong, thick, subrotund; spire de¬ 
pressed ; aperture nearly round ; lip almost continuous, having 
a slight groove only at its junction with the body; no umbilicus. 
Neritoides litteralis. — The Shore Neritoides. 
Plate LXXXVI. fig. 24. 
Smooth, covered with an olive-green, yellow, brown, or other 
coloured epidermis, sometimes beautifully banded or chequered 
beneath it; inside generally purplish-brown; body very large ; 
spire very short and depressed. Five-eighths of an inch long. 
Inhabits the shores of Northern Europe. 
Genus 58.—NE RITINA.— Lamarck. 
Generic Character. —Shell thin, semiglobose, or ovate, flat¬ 
tened below; without an umbilicus; aperture semicircular; in¬ 
ner 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. 
Neritina jluviatilis .— The Fresh-Water Neritina. 
Plate LXXXV. fig. 14. 
Shell small, oval; back convex, smooth, white, variously 
speckled with black, or dark brown ; spire inclined, lateral; lip 
slightly denticulate. One third of an inch long. Inhabits the 
rivers and streams of Europe. 
Genus 59.—NAVICELL A.— Lamarck . 
Generic Character. —Shell elliptical or oblong; convex above, 
concave beneath; spire erect, the margin always inflected ; outer 
lip flattened, acute, angulated, and destitute of teeth ; aperture 
provided with a solid flat operculum, having a lateral point. 
