1920.] N. Annandale : Indian Hydrohiidae. 45 



penetrate to the internal surface. The radula closeb^ resembles 

 that of Alocinma ; but the laterals have the central denticulation 

 much enlarged and bear a distinct prominence on their disc. 

 The two subgenera may be distinguished as follows : — 



1. Shell more or less elongate, acuminate, with the main 



axis of the spire and that of the body-whorl in the 



same straight line and the mouth vertical . Hydrobi aides 



is.s.) 



2. Shell globose, with the spire short and oblique, almost 



neritiform, with the mouth very oblique ... Paranerita, 



nov. 



The type-species of Hydrohioides {s.s.) is Bithynia tunita, 

 Blanford; that of Paranerita, Hydrohioides physcus, Annandale, 

 the only known species. I can find no structural difference 

 between the animals of the two subgenera. 



The peculiarities of the lower part of the shell in both sub- 

 genera seem to be correlated with a very definite, probably seasonal 

 and recurring period of arrested growth. The varix in those species 

 in which it persists represents the last period of rest, after which 

 there is apparently only one more growth-period. In several shells 

 in Nevill's series of his Bithynia moreleiiana, which must be referred 

 to this genus, a well-defined varix is present at some distance from 

 the mouth, but beyond this ]3oint the shell is very thin and the 

 outer lip is sharp, proving that the animals were killed during a 

 period of active growth. 



The porcellaneous appearance of the mouth and the outlines 

 of the shell give the species of Hydrohioides {s.s.) a superficial 

 resemblance to those of Pachydrohia, Crosse and Fischer, an Indo- 

 Chinese genus ; but the structure of the operculum is very different 

 and the male organ of Pachydrohia differs in being simple and 

 without a lateral process. The shell of H. {Paraneiita) physcus, 

 on the other hand, resembles that of Julliena of the same authors 

 and from the same region, but here again there are the same struc- 

 tural differences in the animal. 



Genus Sataria, nov. 



The shell is moderately small and thick, almost trochiform, 

 with swollen whorls. The umbilicus is patent but not deep and 

 is approached from the anterior border of the mouth by a broad, 

 deep, oblique groove. The peristome is continuous, uniforml}- 

 thickened internally, prominent and produced to a point both above 

 atid below. The sculpture of the shell consists of fine but distinct 

 spiral grooves. The operculum is calcareous, of ovate outline and 

 rather smaller than the mouth of the shell. The operculum is 

 stout and marked with strong concentric ridges externally, the 

 nucleus being central ; internally it is convex and without sculp- 

 ture. The radula resembles that of Bithynia but the denticula- 

 tions of the teeth are blunter and there is a quadrate process on 

 the disc of the central tooth. Nothing is known of the soft 

 parts. 



