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



Genus Amnicola, Gould and Haldeman. 

 Subgenus Aloclnma, Annandale and Prashad 



lyiy. Alocinma, Annandaleand Prashad, Rec. Iiid. Mns. Will, p. 2,V 

 1920. Alocinma, Annandalf, ibid., XIX, pp. 43, 44, 



I still think it more convenient to regard Alocinma as generi- 

 cally identical with Amnicola, for the soft parts and radula are 

 closely similar and the operculum intermediate between that of 

 Amnicola [s.s.) and that of Pseudainnicola. 



Amnicola (Alocinma) orcula (Frauenfeld). 



1876. Bithynia oratla, Hanle)- and Theobald, Condi, hid. pi. .\.\.\viii, 



figs. 8, 9. 

 1885. Bithynia orcula, NeviU, Hand List Moll. Ind. Miis. 11, p. 36. 

 1919. Amnicola {Alocinma) orcula. Annandale and Prashad. op. cit., 



p. 24. 



Frauenfeld was the first to describe this species, though he 

 gave it Benson's name. It is one of the commonest molluscs of 

 the Indo-Gangetic plain and is replaced in Peninsular India by A . 

 stenolhyroides (Dohrn), which is hardly more than a local race. 

 Manipur is apparently the limil of the range of the species in a 

 south-easterly direction. It has not been found in Burma. 

 The radula, operculum and male organ closely resemble those of 

 A . sistanica. The last, however, varies in the proportions of its 

 different parts, as it does also in other members of the family, in 

 accordance with its condition when the animal is killed. 



Nevill has named several "varieties" and " sub varieties ". 

 Of these the only one that concerns us here is his " var. producta 

 (? dist. sp.)". It has a much narrower and more elongate shell 

 than the forma iypica, with which it often occurs, but in my 

 opinion is no more than an aberration. 



A. orcula is abundant in ponds and swamps in the Manipur 

 valley. In the day-time it is to be found both on mud at the 

 bottom and among water-plants, but in the evening rises to the 

 surface and crawls, shell downwards, on the surface-film. The form 

 producta is not uncommon with the forma iypica in Manipur. 



Genus Digoniostoma, Annandale. 



1920. Digoniostoma, .\nn:md;i\e, Ind. Journ. Med. Research, N'lll.p. 104. 



The chief characteristics of this genus have already been 

 mentioned in the key on a preceding page. I did not separate it from 

 Bithynia, Leach, in my recent paper on the Indian species confused 

 under the name of that genus, though I was aware of certain 

 peculiarities in the shell, but I have to thank Mr. A. S. Kennard 

 for drawing my attention to certain of the differences. These 

 lie in the structure of the peristome. The lip is not so distinctly 

 thickened as in Hydrohioides and a supplementary varix is never 

 present. The columellar callus is thick, broad and prominent and 

 always has a laminated appearance. At the point at which it 



