622 Rcxords or the Indian Museum. [Vol. XXII, 



only from the Ganges Valley and Manipur. Hippeutis (?) timbili- 

 calis has a similar range but was described from Sylhet. It is 

 the most abundant Planorbid in the .Manipur Valley, but is scarce 

 in that of the Ganges. The range of Segnientina calathns extends 

 from Seistan, beyond the western frontiers of the Indian Empire, 

 to Upper Burma and Sumatra. The two species of Anc\'hts have 

 both been found in Ceylon as well as in Peninsular India. The 

 origin of most of these species is probably to be sought in the 

 Gangetic plain or Peninsular India, but the species assigned doubt- 

 fully to Hip pent is may be of Assamese origin This is still more 

 probable of Acrostoma variiibilis , which is common throughout the 

 plains of Burma and Assam l?ut in India west of the Bay of 

 Bengal ejctends onl}' for a short distance up the Gangetic system, 

 where its numerous varieties and phases have usually a dwarfed 

 facies and do not exhibit the same sturdy appearance that they 

 do further east. 



The "Indian" element among the freshwater Gastropods 

 of Manipur may thus be regarded as of mixed origin, partly 

 Indian in a strict sense, partly immigrant into India proper from 

 further east. But on the whole the former element predominates. 



The aquatic fauna of Assam has less of an indigenous element 

 than that of the Ganges Valley and is, indeed, largely compounded 

 of a mixture of that of India proper and chat of Burma. The 

 indigenous element, however, is not wholly wanting in the Brahma- 

 putra watershed, and to this element we must assign three of the 

 -Manipur Gastropods, viz. Digoniostoma pulchelluju, which is 

 hardly more than a local race of the Gangetic D. ceramcopoma, 

 Pachyiabra niaura, which bears much the sam.e relationship to the 

 Gangetic P. globosa, and Camptoceras lineatum. This last species 

 was originally discovered in what is now the Dacca District of 

 Eastern Bengal, at a place beyond the political frontiers of As-am, 

 but within the limits of the Brahmaputra system. It is note- 

 worthj' as the onh^ species of its genus that has been found at 

 more than one place, and its rediscovery in Manipur has, there- 

 fore, some interest. The species is abundantly distinct from any 

 other. Its nearest ally is C. subspinosuin from the valley of 

 Kashmir in the western Himalayas. 



Two Gastropod species on our list have as yet l^een found 

 only in the Manipur Valley and at Dimapur in the plains of North- 

 eastern Assam just north of the Naga Hills. They are Limnaea 

 ovalior and Ancylus viola. 



The isolation of the Manipur Valley readers the existence in 

 it of endemic species by no means surprising. So far as our 

 knowledge goes, live Gastropod species on our list belong to this 

 category, namely Digoniostoma textum, Vivipara crassispiralis, 

 V. micron, Pahidomus pustulosa, Succinca elcgantior Half of 

 these belong to the genus Vivipara and it is worthy of mention 

 that each of the two species belongs to a different section ' of the 



' Rec. fiui. Mtis. XIX, pp. Ii2-ii.| (1920). 



