1921.] Manipur Molluscs. 557 



examination of their opercula. Probably the true Paludina sia- 

 mensis of Frauenfeld is also the young of some allied species. 



Family AJIPULLARIIDAE. 

 Genus Pachylabra, Swainson. 



The use of the name Pachylabra for the Oriental and African 

 species of Ampullariidae has been discussed bj' Kobelt in the curr- 

 ent edition of Martini and Chemnitz's Conch. Cab., pp. 44-46 

 (igii). The genus is distinguished from the American Anipnllaria 

 by the structure of the operculum and the inhalent siphon. The 

 former in Pachylabra is massive and calcareous with a coarse exter- 

 nal horny covering. The siphon when contracted is a prominent 

 fold forming an incomplete tube not verj' much longer than its 

 transverse diameter. When expanded it is a funnel shaped struc- 

 ture, considerably broader than long. 



This genus is represented in the Manipur Valley by a single 

 ■ species (P. niaura, Reeve), which is common throughout the plains 

 of Assam. In the Manipur Valley, however, it was found only in a 

 few ponds in the immediate vicinity of the capital. The question 

 naturally arises, may it not have originally been introduced bj' 

 man, either as food or accidentally ? The Manipuris even now eat 

 some kinds of molluscs and the Naga tribes of the surrounding 

 hills are fond of all the larger freshwater species. P. manra, how- 

 ever, is well within the geographical limits of its range in Manipur, 

 for it is found in the valley of the Brahmaputra on the one hand 

 and on the Shan Plateau on the other. 



Pachylabra maura (Reeve). 



185(1. Ampiillaviit maura, Keevc, Co)ich. Icon., pi. xiii, fig. 57. 

 1887. Anipnllaria maura, Nevill, Cat. Moll. hid. Mits. E, p. 5. 

 1885. Ampiillaria maura, id.. Hand List Moll. Ind. Mus. II, p. 4. 

 1918. Ampullaria winkleyi, Annandale {iiec Pilsbry), J^ec. Ind. Mns. 

 XIV, p. 1,^8, pi. xii, fig. 10. 



My identification of specimens from the North Shan States as A . 

 winkleyi was certainly incorrect and I can find no constant differ- 

 ence between them and shells from Assam except that they are paler 

 and brighter in colour. Of the true A. ivinkleyi I have recently 

 examined a shell from Patalung in Peninsular Siam.' Its minute 

 spiral sculpture is much better developed and its shape different. 



All the specimens examined from Manipur are small and have 

 the shell very dark. They agree, however, precisely with some 

 individuals from Dimapur and from Gauhati on the Brahmaputra. 



The species is probably no more than an eastern race of P. 

 globosa (Swainson), the common Ganges species. Nevill, however 

 (op. cit., 1887, p. 5), keeps it distinct on account of its " wider um- 

 bilicus, more contracted aperture with dark-coloured margins, more 

 produced spire and thinner shell." I doubt whether these dif-- 

 ferences will be found to be constant, but until the Indian species 



.\nnandale, Journ. Nat. Hist. Sac. Siam IV, p. 45 (1920). 



