578 Records of the Indian Museum. [Vol. XXII, 



bases. Penis long, a simple cylindrical tube; 

 penis-sheath similar, no retractor muscle ... Indoplanurbis. 

 B. Shell thin, as a rule small, if more than i cm. in maxi- 

 mum diameter with the whorls flattened below, 

 Branchial process simple, 

 i. Shell always, less than i cm. in diameter, appar- 

 ently de\tral (though the animal is sinistral), 

 with the whorls convex above and below but 

 flattened as a whole, usually with a peripheral 

 keel. Radula like that of Plaiiorbis. Penis 

 relatively long, provided with a hornj' stylet ; 

 preputium of complicated structure ; a single 

 retractor muscle present ... ... Gyrau/iis. 



u. Shell small or of moderate size, flattened below, 

 without internal teeth or folds. Radula ex- 

 tremely small with minute teeth ; laterals 

 twinned. Penis relatively short and stout with- 

 out a horny stylet ... ... ... Hippeufis'! 



iii. Shell small, resembling that of last genus but 

 usuall)- with hard enamel-like vertical ridges. 

 Radula as in Gyraii/iis but with the lateral and 

 marginals more numerous. Penis long and 

 narrow, asymmetrical with horny stylet; penis- 

 sheath with a pair of lateral lobes at its upper 

 extremity : preputium well developed with a 

 single retractor muscle... ... ... Seginentinn. 



II. Shell ovate or almost cylindrical, sinistral (BuUininae). 

 Shell small and thin, elongate, with the suture remark- 

 ably broad, deep and oblique. Animal with a simple 

 branchial process, and a well developed left epipodial 

 leaf-like lobe, which can be spirally coiled to form a 

 complete anal funnel. Radula like that of Gyraiilus 

 but with broader denticulations on the teeth. Penis 

 broad and stout, without a stylet ... ... Caiuptocei-as. 



Indoplanorbis, gen. nov. 



1915. Plaiiorbis. Preston, Fauna. Brit. hid. Fresliiv.-MolL, p. J 15. 



The adult shell is relatively large and thick and closely resem- 

 bles that of Plano^bis {s.s ). The whole is discoidal, but the 

 whorls are convex and the suture deeply impressed. The aperture 

 is ear-shaped, with the broader end {morphologicall}^ the lower 

 extremity) uppermost when the shell is held with the mouth on 

 the left. The young shell resembles that of Physa and is ovate, 

 with the upper extremity flattened and the lower somewhat point- 

 ed, the spire being nearly flat. 



The animal is sinistral. Its foot is relatively broad and short, 

 leaf-shaped, broadly rounded in front and pointed behind. The 

 head is very broad and has its lower margin expanded and flat- 

 tened. The tentacles are elongate and filiform. The eyes lie at the 

 inner base of the tentacles and are completely sessile. The mouth 

 opens on the lower surface of the head in front of the foot. 



The jaw is narrow and has lateral pieces of the usual type. 

 The radula is broad having more than 20 longitudinal rows of 

 marginals. The central is relatively large and bicuspid. The 

 laterals are tricuspid, short and broad ; the free lobe equals the 

 base in length. They closely resemble those of Limnaea. The 

 transition between the tricuspid laterals and the pectinate margin- 



