1918.] N. Annandale : Molluscs of the Inle Lake. 121 



Tenasserim which belong to the same species. They are labelled 

 " Bithynia subnassa, Nevill." This is apparently a nonten nudum. 

 They only differ from the Shan types in being slightly larger, the 

 largest being about 9 mm. long. 



Type-specimens. M. 11127-9/2, Zoological Survey of India {Ind. 

 Mus.). From near Fort Stedman. 



Hydrobioides nana, sp. nov, 

 Plate xiv, fig. 3. 



Shell conoidal, moderately elongate, thick, transparent, brownish, 

 with the spire darker than the body-whorl, smooth and polished on the 

 surface, narrowly umbilicate, with the spire straight, blunt ; with 4 

 whorls ; whorls swollen, suture somewhat impressed ; aperture large, 

 ovate, oblique, bluntly pointed posteriorly ; peristome thickened, 

 continuous ; no varix on the body-whorl. 



Measurements of specimen. 



mm. 

 Length of shell ... ... ... ... ... 2-75 



Breadth of shell ... ... ... ... ... 1-75 



Length of aperture ... ... ... ... 1-25 



The operculum is ovoid, thick, whitish, translucent, with the central 

 area marked off by a distinct external ovoid ridge in the adult, with 

 very numerous fine concentric striae. 



From young shells of H. nassa those of this species can be recognized 

 by their more swollen whorls, less pointed aperture and umbilicate 

 condition, and especially by the structure of the operculum, which 

 in young nassa is distinctly spiral. 



We found about half a dozen specimens of this species at the edge 

 of the Inle Lake at Fort Stedman and in a small pool in the marsh at 

 the northern end of the lake. I have been unable to examine the 

 anatomy. 



Type-specimen. M. 11289/2, Zoological Survey of India {Ind. 

 Mus.). 



Hydrobioides physcus, sp. nov. 

 Plate xiii, figs. 8, 8a, 9 ; plate xiv, figs. 5, 5a. 



Shell thick, translucent, white or pale yellow, globose, subneritiform, 

 sub"Umbilicate, with the spire short, pointed, directed obliquely back- 

 wards ; suture not strongly impressed ; 4| whorls, the body-whorl 

 relatively very large and swollen. Aperture patent, oblique, almost 

 as broad as long, with the outer lip slightly produced outwards, not 

 much thickened, as a rule brownish ; columellar callus very broad, 

 longitudinally striate, strongly convex. The first 3| whorls rounded ; 

 basal whorl with a strong but blunt ridge running round its dorsal 

 aspect a short distance below the suture and as a rule broken up more 

 or less distinctly by longitudinal grooves ; other almost obsolete spiral 

 ridges sometimes to be detected running parallel to it on the central 



M 2 



