268 RISSOID A. 
Shell very long, with numerous slowly-enlarging, convex 
whorls; outer lip with a short sinus above. Operculum unknown. 
TricuLA, Benson. 
Distr.—l sp. Fresh water, India. TJ. Montana (1xxii, 63) 
inhabits the river Kamaan, in India. 
Shell elongated, smooth, subperforate ; aperture ovate, rather 
narrow; inner lip thickened. Operculum corneous, nucleus 
very small, close to the base. 
The animal has an elongated proboscis and filiform tentacles, 
with the eyes at their outer bases; in its thickened inner lip, 
the shell somewhat resembles Paludomus, but it is distinguished 
by its elongated spire and truncated apex. 
PACHYDROBIA, Crosse and Fischer. Shell imperforate, oblong- 
ovate, rather thick; spire moderate, with impressed suture ; 
aperture semicircular; peristome sinuous, continuous, thickened. 
Operculum subovate, thin, corneous, paucispiral. 2 sp. Fresh 
rater, Siam, Cambodia. TJ. paradoxa, Cr. and F. (1xxii, 64). 
Pyreuta, Christofori and Jan. 
Syn.—Pyrgiscus, Herrmansen. 
Distr.— Mountain streams, Europe, West Indies, South 
America. P. helvetica, Mich. (1xxii, 65). 
Shell elongated, turreted , imperforate, four whorls, carinated ; 
aperture oval, effuse anteriorly, outer lip not thickened. Oper- 
culum corneous, with projections on the outer margin corres- 
ponding to the concavities of the carinz of the shell. 
Foot narrow, obtuse, subbilobate in front, somewhat pointed 
behind, tentacles slender. 
DIANA, Clessin. First whorls very small, last three nearly of 
equal size. P. Thiesseana, Clessin (1xxii, 66). 
PALADILHIA, Bourg. 
Distr.—T sp. Europe. P. pleurotoma, Bourg. (1xxii, 67°. 
Shell minute, turreted, smooth ; aperture expanded, peristome 
continuous, sinuous above and below ; axis perforated. 
Rivers of France. Only dead shells have been collected, so 
that the animal and operculum are unknown. The systematic 
position of the genus is doubtful. The Pleurotomoid sinus of 
the aperture is its remarkable feature. 
LartettA, Bourg. 
Named after the paleontologist, Edward Lartet. 
Syn.—Micromelania, Brusina. Goniochilus, Sandberger. 
Distr.—9 fossil, 10 recent sp. France. L. Bourguignatt, 
Palad. (lxxii, 68). 
Shell solid, spire elevated; peristome continuous, partly 
detached from the body-whorl on the left side ; perforated. 
