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th 
No 
Records of the Indian Museum. [Vor XVIII, 
Benson in his original description described the genus as 
belonging to the Melaniidae, basing his argument partly on shell- 
characters, which according to him showed the same relationships 
to Melania s.s. as ‘‘ certain Egyptian and Syrian species of Palu- 
domus’’ bore to that genus; and partly on anatomical grounds, 
the animal being, according to him, Melania-like. In this sup- 
position he was followed by Gray and H. and A. Adams, but Brot in 
his revision .of the Melaniidae, differing from them, stated that the 
genus was probably referrable to the Paludinidae. Benson in his 
subsequent work slightly elaborated his original arguments, and 
considered Brot’s position untenable owing to the ‘‘ very funda- 
mental difference between the concentric operculum of Paludina 
and the subspiral one of Tvicula” ; he again laid stress on the 
resemblance of the animal of Tvicula to that of Melania. Stimpson, 
Stoliczka, Blanford and Nevill considered Tricula to be a Rissoid 
genus. Fischer in doubtfully placing it amongst the Hydrobtiidae 
compared it with Acicula, a genus of land-molluscs, and re- 
marked, ‘‘ I,a classification de ce genre est embarrassante.”” He 
had, however, come to a nearly correct conclusion. Preston 
followed him in assigning Tyvicula to the Hydrobiidae, or what 
he calls Paludestrinidae. I have pointed out above the resem- 
blance between the shell of T. montana and that of the various 
species assigned to the genus Bithinella. ‘The resemblance between 
its animal and that of the genus Melania, on which Benson laid so 
much stress, is only superficial and his own description does not 
show any differences between the animal of Trvzcula and that of 
any other Hydrobiid. Assuming, therefore, that the genus is a 
true Hydrobiid and that there is no difference between it and the 
genus Bithinella, Moquin Tandon, the name Tvicula, Benson will 
have priority over Moquin Tandon’s. 
It may be noted here that the Indian brackish-water species 
referred to as Bithinella miiiacea in a recent paper! by Dr. Annan- 
dale and myself is not assignable to the genus Tvzcula, but has 
relationships with the genus Stenothyra, Benson. 
I have here to express my indebtedness to Dr. N. Annandale 
for pointing out to me the exact status of the genus Tyvicula and 
for the help he has so generously given me in clearing up its 
synonymy. 
Tricula palmyrae (Dautzenberg). 
1918. Bithinella palmyrae, Annandale, op. cit., p. 162. 
The only specimens of this species are the shells referred to in 
Dr. Annandale’s paper cited above. I have carefully compared 
them with Dautzenberg’s description and figure of the species and 
can find no differences. 
Genus Bithynia, Gray. 
In the Mesopotamian collection this genus is represented by 
two species: (i) B. badiella, a species common in Palestine and 
| Rec. Ind. Mus., XVI, p. 248 (1919). 
