6i4 



Keconis of the Indian Museum. [Voi,. XXII, 



ably based on immature specimens. In the Manipur collection 

 there are specimens from small streams near Potsengbani and from a 

 large shallow artificial tank called Ningyang Pukri at Imphal. All 

 these specimens closely agree with Prime's description and figures 

 and are sexually mature. The shell in this species is rather small 

 and apparently does not grow larger than 15 mm. in length. 

 The pallial line is a regular curve and does not show any sinus. 



The soft parts resemble those of the other two species des- 

 cribed already, but differ in the poor development of the siphonal 

 retractor muscles and the siphons. 



Genus Sphaerium, vScopoh. 



lyou. Sphaen'iini, Preston, op. cit., pp. 223, 224. 

 Three species of this genus have hitherto been described from 

 India ; of these S. indicuin is a widely distributed species both in 



KiG. 33. — Hinge teplh of Sphaerittm. 

 .\. S. ittdiciim, Deshayes. B. S. atisteni. Frashad. 



the plains and in the Himalayas, while 5. avanuni is only known 

 from Ava and Pegu in Burma. The third species, S. montanum, 

 Tapparone-Canefri,' is only known from Burma but the original des- 

 cription is not sufficient to identify this species. In the collections 

 of the Indian Museum I have found specimens of an undescribcd 

 species from the Naga Hills and Manipur, probably from the collec- 

 tions made in these parts by Lt.-Col. H. H. Godwin-Austen. The 

 three species before me may be distinguished from one another by 

 the use of the following key : — 



1. Shell larore, g'5 mm. in length, much swollen, wiih very 



prominent urnbones and with strongly impressed con 



centric sculpture ... ... . . 5. avaniim. 



2. Shell smaller and not so much swollen as in 5. avaniim. 

 a. Shell ovato-rhomboid, thin and translucent, with 



the umbones only slightly prominent and with 



very faint sculpture ... ... ... S.indicum. 



I Ah7i. Mus. Civ. star. Nat. Geiiova (2) VII. p. 356 (18S9), see Addendum, 

 p. 630. 



