MOLLUSCA. 
409 
Valvala piscinalis .— The Pond Valvata. 
Plate LXXXVI. fig. 4. 
Globular, conoid, somewhat trochus-shaped, deeply umbili- 
cated ; apex obtuse ; longitudinally wrinkled; covered with a 
greenish-yellow epidermis. One-fourth of an inch long. Inha¬ 
bits the rivers and lakes of Europe. 
TRIBE VIII.-MELANIDES. 
Fluviatile operculated shells ; with the margins of the aper¬ 
ture disunited; the outer lip edged; the animals do not respire 
in the water, and are provided with two tentacula. 
Genus 63.—PIRENA. — Lamarck. 
Generic Character. —Shell turrited; aperture longitudinal; 
outer lip acute, with a distinct sinus at the base, and another at 
its junction with the body; base of the columella turned to¬ 
wards the right; provided with a horny operculum. 
Pirena terebralis. — The Dark Pirena. 
Plate LXXXVI. fig. 7. 
Subulate, longitudinally striated ; outer lip expanded; covered 
with a deep black-brown epidermis; aperture white. Three 
inches long. Inhabits the rivers in India. 
Genus 64.—MEL AN OPSIS.— Lamarck. 
Generic Character. — Shell turrited; aperture ovate-oblong, 
entire ; columella with' a callosity above, truncated at the base, 
and incurvated ; the outer lip separated from the inner one by a 
sinus ; aperture with a horny operculum. 
Melanopsis Icevigata. — The Polished Melanopsis. 
Plate LXXXVI.|fig. 28. 
Ovate, conical, smooth, of a chestnut-colour. Three-fourths 
of an inch long. Inhabits the rivers of the Archipelago. 
Genus 65.—M E L A NIA.— Lamarck. 
Generic Character. — Shell turrited ; aperture entire, ovate or 
oblong ; effuse at the base ; columella smooth, and incurvated ; 
aperture with a horny operculum. 
