ig2i.] Manipur Molluscs. 555 



pyriform. The central boss on the internal surface is situated 

 nearer the inner than the outer margin. It is highly polished but 

 its base is marked with fine radiating, iridescent ridges. The area 

 surrounding it is smooth, hut fine radiating lines proceed down on 

 it from the boss. 



The radular teeth are figured in fig. 3, on p. 544. They exhibit 

 no essential difference from those of Vivipara. 



The animal has the generic characters. It is rather less bright- 

 ly coloured than most species of Viviparidae, the body being sooty 

 black and the minute spots with which it is covered being dull 

 yellow and very small. The tentacles are very long and thin and 

 the foot is remarkably stout. Fig. 7 shows the outstanding 

 differences between the living animal and that of V . oxytropis, 

 which in most respects is a typical Vivipara so far as the soft 

 parts are concerned. 



Type-specimens.— 1^0. 2300 Zool. Surv. Ind. [Ind. Mtis.). 



Geographical Range. — The type-specimens from the Asiatic 

 Society's collection are labelled as being from Sylhet, but they 

 agree so closely with shells from the more open part of the 

 Loktak Lake ' that I think this locality is probably incorrect. 

 The species is not represented, so far as I am aware, in any 

 recent collection from Sylhet and it must be remembered that 

 at the time when Benson's collection was made Sylhet was on 

 the way to Manipur. The true range probably extends from 

 the Manipur Valley through Upper Burma to the Southern Shan 

 States, Yunnan and Cochin China, Nevill records young speci- 

 mens from the Philippines, but in view of their immaturity 

 the record is open to doubt. 



In Manipur no less than four phases can be distinguished, 

 one of which, at one end of the series, is the jorina typica. 

 while another, at the other end has received the varietal name 

 ampullijormis. I shall describe the phases under English names. 



The Open-water Phase (=foriiia typica) : plate V, figs, i, 2. 

 The shell is very large, globose, thin and translucent and is of 

 a bright olive-green colour externally and only slightly washed 

 with bluish white internally. The aperture is subcircular, the outer 

 lip strongly arched and very thin. The sculpture is very fine and 

 delicate and if varices occur on the body-whorl, as is often the case, 

 they are poorly developed and as a rule not blackened. This phase 

 is found in the more open parts of the L,oktak Lake. 



The Marginal Phase : plate V, fig. 3. The shell is thicker, 

 heavier, more opaque and coarser than in the last phase and, 

 though individuals grow at least as large, is usually smaller. 

 The spire is relatively longer and not quite so broad at the base, 

 the whorls are not quite so convex and the aperture rather 



i Specimens of this phase are not difficult to obtain as the)- are brought up 

 in hundreds by tlie fishermen in their nets. I have to thank Mr. C. Forster 

 Cooper, Superintendent of the Cambridge University Museum, for examining 

 the specimens in the Benson collection. He informs me that they also are 

 labelled " Svlhet." 



