1 921. J Manipiir Molluscs. 553 



The animal differs from that of Vivrpara in the greatly thick- 

 ened and highly muscular free edge of the mantle, the sphincter 

 muscle running along which is very strong and conspicuous. The' 

 radula is identical witli that of Vivipara. 



Typc-species^ — Paludina Iccythis, Benson. 



Geographical Range. — The range of the genus probably ex- 

 tends from the Manipur Valley through Upper Burma and possibly 

 Tenasserim to Yunnan and Cochin China and thence across China 

 to the Philippines, Celebes, Formosa and Japan. But I am not 

 quite sure as to the generic identity of some of the Far Eastern 

 species. In all those from China and Japan I have examined (ex- 

 cept specimens of the type-specits from Yunnan) the operculum 

 differs in having the ring-shaped area round the central boss on 

 the internal surface much more strongly roughened and scar-like 

 than in L. lecythis. 



Anatomically the new genus closely resembles Vivipara, as. 

 indeed, do all the Asiatic genera of the family, but the structure 

 of the mantle-edge and its sphincter is characteristic' 



The strong mantle-sphincter has probably a definite function 

 to perform, viz. that of protecting the branQhi'al" chamber from 

 the entry of parasites."^ As my assistant Mr. Amin-ud-Din pointed 

 out to me at the Loktak Lake, almost e\-ery specimen of Vivipara 

 oxytropis we examined there was infested b}^ a leech of the genus 

 Glossosiphonia, over 30 individuals of which were sometimes found 

 in the branchial chamber of a single specimen, while the branchial 

 chamber of Lecvthocojicha from precisel}' the same habitat was 

 invariably empty. The contraction of the powerful muscle must 

 close this chamber much more effectively than that of the com- 

 paratively feeble muscle in V. oxytropis. 



Lecythoconcha Iccythis (Benson). 

 (Plate V and plate VI, figs, x, 2.) 



185(5. Paludina lecythis, Benson, Jonrn. As. Soc. Bengal V^ p. 745, 

 1852. Paludina ampiiUiformis, Eyciou.v and Souleyet, Voy. ' Bonite,' 

 Zool., p. 540, pi. xxxi, figs. 25-27. 



1876. Paludina lecythis and var. ampulliformis, Hanley and Theo- 



bald. Conch. Ind., pi. Ixxvi, fiqs. 6, 7. 



1877. Palndina chinensts varr. amptillifovmis and lecythis, P. siamen- 



sis (in part), Nevill, Cat. Moll. hid. Mus. E, pp. 25, 36. 

 1885. Paludina chinensis varr. ampulliformis and lecythis, P. siam- 

 ensis var. bui-tnanica, id.. Hand List Moll. Ind. Mus. II, pp. 

 20, 26. 



The shell is of large or very large size, thin, of a uniform 

 olive-green when fresh but often fading to brown, globose, narrow- 

 ly perforate. There are 4J or 5 whorls. The apex is acuminate 



1 Annandale, Rec. Ind. Mus. XIX, p. 114, fig. 3 (1920). 



■^ Major R. B. S. Sewell found the mantle of both L. lecythis and V. oxytro- 

 pis from the Loktak Lake and ponds at Imphal infested with an encysted Trema- 

 tode {Leucochloridiuin), but the orifice of the cyst was always on the external 

 surface of the mollusc. I have found a minute parasitic mite among the gill- 

 filaments of L. lecythis. 



