1920.] N, Annandai,t5 .• Indian Freshwater Gastropods. 11 1 



No. II — The Indian Genera of Viviparidae. 



By N. AnnandaIvE, D.Sc, F.A.S.B. 



Until recently all the Indian species of this family have been 

 placed in the genus Vivipara, Montfort ; but in 1918' I separated 

 certain forms from Upper Burma and the Shan States under the 

 name Taia, while still more recently* I have described three 

 fossil or subfossil subgenera of this genus from the same coun- 

 try. In the present paper I give reasons for regarding one of these 

 {Temnotaia) as generically distinct and put on record the occur- 

 rence of a living species in Upper Burma. An examination of the 

 animal of Benson's Paludina lecythis proves that it and its allies 

 must also be separated from Vivipara. I propose for them the 

 new generic name Lecytho concha. 



Key to the Indian Genera of Viviparidae. 



1. Columellar callus of shell broad and plate-like. 



A. Sculpture usually consisting- of prominent nodular, 



squamose or spinulose spiral ridges and of coarse 

 longitudinal striae. Operculum with an internal scar 

 of oval or ovate outline and without a rounded boss 

 in the centre of the scar. Mantle'of adult with a 

 rather feeble sphincter muscle and a smooth or lobular 

 margin ... ... ... ... Taia. 



B. Shell smooth or with incised spiral lines. Operculum 



as in Taia. Soft parts and radula unknown ■■ ... Temnotaia. 



2. Columellar callus not plate-like. Sculpture minute or includ- 

 ing smooth spiral ridges. 



A. Shell of small or moderate size, conical or conoidal. 



Operculum as in Taia. Mantle with the sphincter 

 muscle moderately developed and prominent ; its 

 margin bearing in the young well-developed digiti- 

 form processes, which persist in the adult of some 

 species ... ... ... ... Vivipara. 



B. Shell large and globose. Operculum with a well- 



defined funnel-shaped pit on the external surface cor- 

 responding to a smooth, prominent rounded boss 

 in the centre of the internal muscular scar, which 

 is ring-shaped and poorly developed. Mantle 

 sphincter very strong and prominent ; mantle itself 

 greatly thickened and highly muscular, bearing 

 three digitiform processes in the young, smooth in 

 the adult ... ... ... ... Lecythoconcha. 



An examination of the mantle in these genera shows that it 

 provides good generic characters. In all it is highly vascular, but 

 in Taia and Vivipara it is thin and has a comparatively feeble 

 musculature, while in Lecythoconcha it is much thickened and has 

 both longitudinal and transverse muscles very strongly developed. 

 In all three genera the transverse muscles are congregated on the 

 outer surface a short distance above the margin. It is prob- 

 able that all the Oriental species of the family have digitiform pro- 



i Rec. Ind. Mus., XIV, p. 123 (1918). 

 "^ Rec, Geol. Stirv. Ind., L, p. 231 (1919). 



