TRACHELIPODA, 87 



Genus 62 — VAL VAT A— 3Iu&r. 



Generic Character. — Shell discoid or conoid; volutions cy- 

 lindrical, umbilicated ; margins united and acute ; operculum 

 orbicular. 



Valvata piscinatis. — The Pond Valvata. Plrte XIII. 

 fig. 4. Globular, conoid, somewhat trochus-shaped, deeply 

 umbilicated ; apex obtuse ; longitudinally wrinkled ; covered 

 with a greenish-yellow epidermis. One-fourth of an inch long. 

 Inhabits the rivers and lakes of Europe. 



FAMILY VII. MELAXIDES. 



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 terehralis. — The WiiiBLE Pirena. Plate XIII. fig. 

 7. Subulate, longitudinally striated ; outer lip expandea ; 

 covered with a deep black-brown epidermis ; aperture w^hite. 

 Three inches long. Inhabits the rivers in India. 



Genus 64.— MELAXOPSIS.— I-a77iarcA. 



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. 



Tlie Melanopsis is distinguished from the Melania, by the columella being 

 5allou3 at the upper part, and the base truncated as in the Auchatina, and 

 differs from the Pirena in having only one sinus, or a widened opening at the 

 base of the shell. 



Melanopsis lavigata. — The Polished IMrlanopsis. Plate 

 XIJI. fig. 28- Ovate, conical, smooth, of a chestnut-colour. 

 h 2 



