2G8 RissoiD^. 



Shell very long, with numerous slowly-enlarging, convex 

 whorls; outer lip with a short sinus above. Operculum unknown. 



Tricula, Benson. 



Distr. — 1 sp. Fresh water, India. T. Montana (Ixxii, 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. 



PACHYDBOBiA, Crossc 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 

 water, Siam, Cambodia. T. paradoxa, Or. and F. (Ixxii, 64). 



Pyrgula, Christofori and Jan. 



Syn. — Pyrgiscus, Herrmansen. 



DUtr. — Mountain streams, Europe, West Indies, South 

 America. P. helvetica^ Mich. (Ixxii, 65). 



Shell elongated, turreted, imperforate, four whorls, carinated ; 

 aperture oval, efluse anteriorly, outer lip not thickened. Oper- 

 culum corneous, with projections on the outer margin corres- 

 ponding to the concavities of the carinse of the shell. 



Foot narrow, obtuse, subbilobate in front, somewhat pointed 

 behind, tentacles slender. 



DIANA, Clessin. First whorls very small, last three nearlj^ of 

 equal size. P. Thiesseana, Clessin (Ixxii, 66). 



Paladilhia, Bourg. 



Distr. — 1 sp. Europe. P. pleurotoma, Bourg. (Ixxii, 61). 



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. 



Lartetfa, Bourg. 



Named after the palaeontologist, Edward Lartet. 



Syn. — Micromelania, Brusina. Goniochilus, Sandberger. 



DiHtr. — 9 fossil, 10 recent sp. France. L. Bourguignaii, 

 Palad. (Ixxii, 68). 



Shell solid, spire elevated ; peristome continuous, partly 

 detached from the body-whorl on the left side ; perforated. 



