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



The young shell removed from the oviduct at full time is 

 identical in all the Manipuri varieties. It consists of 4^ whorls 

 and is conical in outline with the base produced towards the 

 outer margin and pointed. The apex is minutely blunted and 

 retracted, the apical half-whorl lying in a deeply canaliculate 

 suture. Round the other whoils the suture is not impressed. 

 The aperture is regularly rhomboidal, narrow, oblique and some- 

 what elongate. The colour is pale olivaceous green becoming 

 darker and browner towards the apex, which is infuscated. A 

 dark brown spiral band embraces both sides of the suture and 

 is continued round the periphery of the body-whorl, on which 

 a second band of the same colour appears towards the base. 



The sculpture consists of microscopic spiral and longitudinal 

 striae. The latter are strongly curved. There is an obscure, 

 flattened spiral ridge running just below the suture and round 

 the periphery of the body- whorl. 



The Manipuri varieties have much thicker and heavier and, 

 generally speaking, larger shells than the forma typica, which is 

 common in ponds in the Gavgetic delta. This seems to he so in 

 all fluviatile phases of the species In Manipur the varieties 

 occur in the beds of the Imphal River and its tributaries, in 

 muddy water and on a muddy bottom. Apparently they are not 

 found in the swifter, clearer hill-streams. 



The range of A. variabilis as a species extends eastwards 

 Irom the Gangetic Delta, through Assam and Burma and it is 

 represented in the Malay Peninsula, Sumatra and Java by very 

 closely allied forms. Its "varieties" may be mere phases the 

 peculiarities of which are due to some peculiarity (or rather 

 combination of peculiarities) in the environnient, but on this 

 subject little is yet known. The animal is usual ty if not always 

 found on a muddy bottom and obtains its food by scraping the 

 surface with its radula. 



Subfamily PALUDOMINAE. 



Genus Paludomus, Swainson. 



The number of the species and subspecies of this genus 

 found in Burma and Assam is probably considerable, and some 

 species from these countries, notably P. conica (Gray), are parti- 

 cularly liable to form local races. Indeed, specimens of P. conica 

 seem to differ slightly in every stream in which they occur. 

 The whole genus stands, however, in need of revision as far at 

 any rate as the Indian forms are concerned, and it is important 

 that young as well as adult shells should be examined, for in 

 maturity the spire is often so distorted by erosion that the true 

 form of the shell completely disappears. I have been unable to 

 match a Paludomus fairly common in the southern part of the 

 Manipur Valley with any previously described and am there- 

 fore obliged to call it new. Fortunately shells in all stages of 

 development are available. 



