PIRENA. MOLLUSCA. 53 



trochiform, perforated, white ; whorls five, and the apex of the 

 spire obtuse. 2 lines in diameter at the base. Inhabits rivers 

 and ponds in France. Lam. vi. 2, 172. 



FAMILY VIII. MELANIDES. 



Fluviatile shells, with the margins of the opening disunited, and 

 the right one edged ; two tentacula. 



Gen. 62. PIRENA, Lam. 



Shell turreted ; aperture longer than broad, the right margin 

 edged, with a sinus at the base, and another at the summit ; 

 base of the pillar bent towards the right ; operculum horny. 



P. terebralis, Lam. (Strombus ater, Lin.) Shell subulate, black, 

 with smooth contiguous whorls ; aperture white. 3 inches long. 

 Inhabits fresh waters in India. Lister, pi. 115, fig. 10. 



P. aurlta, Lam. (Bulimus, Brug.) Shell turreted, muricate, red- 

 dish, with a row of remote tubercles and a brown band on each 

 whorl ; outer lip contracted at the extremity. 20 lines long. In- 

 habits rivers in Africa. Lister, pi. 121, fig.|16. 



Gen. 63. MELANOPSIS, Lam. Melania, Oliv. 

 Shell turreted; aperture entire, oval, oblong; pillar callous 

 above, truncated at the base, and separated from the right 

 margin by a sinus ; an operculum. 



M. costata, Lam. Shell ovate, oblong, solid, longitudinally ribbed, 

 blackish brown ; whorls seven, the last depressed in the middle. 

 10 lines long. Inhabits fresh waters in Syria. Lam. vi. 2, 168. 



Gen. 64. MELANIA, Lam. Helix, Lin. 

 Shell turreted ; aperture entire, oval or oblong, widened at the 

 base ; pillar smooth, arched within ; operculum horny. 



The shells of this genus are chiefly exotic. Almost all have a brown or blackish 

 epidermis. 



M. amarula, Lam. (Buccinum, Mull.) Shell ovate, oblong, with 

 the whorls transversely keeled above, and the keel spinous ; co- 

 lour chestnut, under a black epidermis ; aperture whitish. 1 \ inch 

 long. Inhabits Indian rivers. Humph. Mus. pi. 35, fig. FF. 



M. decollata, Lam. Shell cylindrical, apex truncated, glabrous, and 

 blackish ; whorls convex, the last obsoletely plicated. 10 lines 

 long. Inhabits rivers of Guiana. Lam. vi. 2, 166. 



FAMILY IX. LYMNJEACEA. 



Shell spirivalve, generally smooth on the external surface, and 

 having the outer margin of the aperture always edged, and 

 not reflected; animal amphibious, generally destitute of an oper- 

 culum, and with flattened tentacula. 



The animals of this family inhabit lakes, ponds, and rivers, and are capable of re- 

 spiring in air or water. 



