1921.J Manipur Molluscs. 575 



side. The body-whorl is relativeh' long and somewhat oblique, 

 about ij times as high as broad; iti inner outline is distinctl}^ 

 sinuate and its anterior extremity is somewhat narrowly rounded 

 and a little expanded. The channel leading to the umbilicus can 

 be seen from the dorsal view. The ventral surface and the aper- 

 ture are in every respect very like those of L. ovalis and L. ovalior, 

 except that they are narrower The sculpture is very like that of 

 L. ovalior, but a little more regular. The height of the type-speci- 

 men is 10 mm., the minimum diameter 6'4, the height of the spire 

 2-5, that of the mouth 7-3 and the maximum diameter of the 

 mouth 45 mm. 



This description would apph' equally well to shells from ponds 

 at Imphal in Manipur, except that they are a little larger and the 

 body-whorl is a little broader. Shells from ponds in the Yawnghwe 

 Vallej' in the vSouthern Shan States resemble the type-specimen 

 even more closely. vShoUs from a pond at Dimapur in the plains of 

 Assam immediately north of the Naga Hills show greater individual 

 variation. In some the difference consists merely in an almost 

 imperceptible reclination of the expansion of the anterior margin 

 and a slight broadening of the penultimate whorl In others, how- 

 ever, which are invariably larger, the spire is decidedly shorter and 

 broader and the body- whorl broader and more oblique. These 

 shells form a connecting link between L. andersoniana and L. 

 ovalior. We will discuss the conditions in which they were living 

 shortly. 



The great majority of Nevill's specimens from Yunnan (includ- 

 ing shells from the same locality as the type-specimen) and also 

 one examined by him (and a number examined by us) from the 

 Southern .Shan States, represent the other phase hitherto unrecog- 

 nized, differing in their smaller size, longer and narrower spire, 

 narrower aperture and body-whorl. In other words their spiral is 

 more tighth' coiled and they are reduced in size. Specimens from 

 a small muddy stream in the Yawnghwe Valley closely resemble 

 these shells. 



Shells from a hill-stream with clear water running rapidly 

 over a stony bed near Bishenpur on the west side of the ^Manipur 

 Valley represent yet a fourth phase. They are still narrower than 

 those from the Yawnghwe stream, of more fragile structure and 

 of a rich golden brown colour. .Some of them are also consider- 

 ably larger. Shells, howe\er, from the same and adjacent streams 

 a little lower down, after they have reached the valley, and from 

 rice-fields irrigated from those streams, agree i^recisely with the 

 Yawnghwe phase. 



There can, therefore, no longer be any doubt that L. ander- 

 soniana is a polymorphic species and that its various forms are 

 correlated with different types of habitat. It is possible to recog- 

 nize four phases, for which it will be convenient to have names, 

 though there is no reason why these names should not be English. 

 We will give a synopsis of the phases and the circumstances in 

 which thev have been found. 



