1021.] N. Annandale & B. Prashad : Gastropods. 3 



Genus Tricula, Benson (1S43). 



1843. Tricula, Benson, Calcutta Journ. \at. Hist., p. 467. 



1851. Bitliinella (in part), Moquin-Tandon, Journ. Concliyliol. II, p. 



239 (footnote"). 

 J892. Bitliinella (in part), Kobelt in Rossmassler's Icon. Land- u. 



S/issivass. Moll. (2), V, p. 36. 



We can find no generic difference between the shell of the 

 Himalaj-an species on which Benson founded his genus Tricula, 

 and those assigned by most recent authors to BithineUa. Some of 

 the figures published by Kobelt are very like the shells of T. mon- 

 tana, the type-species, and we have been able to examine a con- 

 siderable number of European specimens. There is nothing, more- 

 over, in Benson's brief description of the animal to contradict this 

 view. 



T. montana is the only described Indian species that can be 

 assigned to this genus, but we have a second from the Central 

 Provinces as yet undescribed. Nevill's BithineUa iniliacea is irot a 

 Tricula. It is, however, an inhabitant of brackish' water and need 

 not be discussed here. 



Subfamily BITHYNIINAE. 



The great majority of the Indian genera and species belong to 

 this subfamily, in which (except in Amnicola) the operculum is 

 thick and calcareous, the male organ has a lateral appendage, the 

 foot is simple (as it is in all Indian genera of the family) and the 

 central tooth of the radula is provided with several basal denti- 

 culations. 



Genus Bithynia, Leach (1818). 



1920. Bithynia (in part), Annandale, Rec. Ind. Mns. XIX, p. 41. 



In the recent notes on the Indian species of the genus Bithy- 

 nia by one of us, certain characters in the mouth of the shell were 

 overlooked. These, as Mr. A. S. Kennard suggests in a letter, call 

 for reconsideration of the generic position of cerameopoma and 

 other true Indian species. For these the new name Digoniostoma 

 has recently been proposed. There can be no doubt, however, 

 that the Kashmir forms assigned provisionally to B. tentaculata 

 (Linne) and B. troscheli (Paasch) have been placed in the correct 

 genus. In Bithynia the lip of the shell is sharp and not at all 

 thickened and the columellar margin is narrow and ridge-like. 



The type-species is Helix tentaculatus, Linne. 



Genus Hydrobioides, Nevill (1884). 



1885. Hydrobioides (subgenus of Bithynia), Xcvtll, Hand-List Moll. 



Ind. Mus. II, p. 42. 

 1918. Hydrobioides, Annandale, Rec. Ind. Mus. XIV, p. 117. 

 1920. Hydrobioides, id., ibid , XIX, p. 44. 



