1921.J Manipuy Molluscs. 541 



meets the lip a distinct projection is formed. This feature is dis- 

 tinct in D. cerameopoma (Benson), which I propose as the type- 

 species of mj- new genus, in D. lutca (Gra)^), D. piilchelluni (Benson) 

 and the new species here called D. textmn. 



Digoniostoma pulchellum (Benson). 



1S3O. Pahidina pulcliella, Benson, Journ. As. Soc. Bengal V, p. 746. 

 1876. Bitliynia pulcliella, Hanlev and Theobald, Conch, hid. ]il. 



xxxviii, figs. 5, 6. 

 1S85. Bithynia pulchella. Ncvill, Hand List Mull. Ind. Mus. U, p. 

 .35- 

 This species is common in all parts of the plains of Assam but 

 has not been found in Burma. 



The aperture of the shell and the surrounding parts are not 

 quite so characteristic of the genus as in some species, for the 

 columella projects Jess and the umbilicus being practically closed, 

 the channel running forward from it is not so deep or well-defined. 

 The angle at the inner extremity of the lip is also blunted or 

 rounded off. The operculum is distinctly concentric and its exter- 

 nal surface is divdded into several distinct areas bj' prominent 

 concentric ridges. 



Our specimens from Manipur are smaller than those from 

 northern Assam. Several of them are in an interesting stage, 

 having evidently been killed at a period of active growth, in 

 these shells the lip is still thin as in Bithynia and the operculum, 

 which in the fully formed shell cannot be retracted, is drawn in as 

 far as the Ijeginning of the new addition to the shell. I have 

 observed a similar stage in shells of Hydrobioides. 



The soft parts and radula are very like those of the new 

 species {D. textum) now to be described (fig. i). 



D. pulchellum is much scarcer in the Manipur valley than 

 either .1 . orcida or D. texluin. We took it only in ponds at Imphal. 

 In habits it resembles these two species. 



Digoniostoma textum, sp. nov. 



The shell is not more than 8 mm. high and 5 mm. in maximum 

 diameter. It is broadly and irregulary ovate in outline with the 

 apex minutely and obliquely flattened, the whorls moderately 

 convex and not at all angulate externally and the inner anterior 

 extremity pointed and produced obliquely. There are 43- whorls, 

 of which the first whorl and a half are minute and inconspicuous. 

 The others increase evenly but rapidlj^ in size. Thej- are slightly 

 flattened above and more distinct in the inner than in the outer 

 outline. The suture is oblique, linear, and, except at the apex, 

 impressed. The spire is shc.rter than the body -whorl in dorsal view. 

 Its whorls are oblique and transverse, more than twice as broad as 

 deep. The body-whorl in dorsal view is obliquely trumpet-shaped, 

 expanding greatly towards the outer margin. The aperture is 

 relatively long, rnther narrowly oval, slightly oblique, less than | 



