1921.] B. Prashad : Sumatran Molluscs. 505 



Corbicula angulifera, v. Martens. 



1897. Corbicula an^a/ifera, v. Martens, op. cit., p. lid, pi. \-ii. fig?^. 

 28-31. 



A few specimens from fresh-water areas near Medan and 

 Tandjong Djatti, from the Soengei Lepan (Langkat) and a young 

 shell from a streamlet at Timbang Langkat agree closely in shape 

 with one of von Martens' co-types, but the sculpture of all the 

 shells, owing to c-rosion, is very indistinct, and it is, therefore, 

 impossible to be quite certain about their .identification. 



Corbicula pullata, Phil. 



1897. Cofbicnla pullata. V. Martens, op. (-jY., pp. 117. 118. 



I assign a single specimen from a streamlet at Timbang 

 Langkat to this species. This specimen agrees with the description 

 of the species and also with Issel's description and figures of 

 C. dayakoruni, ' which von Martens considers to be only a synonym 

 of Philippi's species. 



Genus Sphaerium, Scopoli. 



So far as I can find no species of this genus of world-wide 

 distribution has so far been recorded from Sumatra. This may 

 be due to the various collectors having overlooked the rather 

 minute shells. The only species known from the adjacent island 

 is P. borneense (Sowerby), but the single shell in the Sumatran col- 

 lection found in a tubeful of Limnaea javanica var. subteres, 

 V. Martens, is quite different from it. As it does not correspond 

 to any previously described form, I have described it here under 

 tlie name Sphaerium ceciliae at the request of Mr. den Doop. 



Sphaerium cecilae, Prashad (sp. nov.;. 



(Plate xiv, fig. 17). 



The shell is ovate, somewhat swollen, subequilateral, rather 

 thick, with the anterior margin small and rounded ; the posterior 

 margin is a little longer than the anterior and is broadly rounded ; 

 the upper and lower margins are regularly curved, the upper 

 curve being deeper than the lower. The umbones are prominent, 

 swollen, recurved inwards and separated from one another in the 

 middle line by a narrow chink. The epidermis is nearlj^ smooth 

 in the umbonal region but has closely situated faint concentric 

 striae below on both the valves. The shell is of a pale horny 

 colour in the umbonal region, but is much darker in the lower 

 region and shows greenish stripes in some places ; the inner surface 

 of the valves is dusky bluish. The right valve has two lamellar 

 laterals on each side, of these the upper is very feeble : there are 



I Ann. Mas. Civ. Star. Nat. Genova, VI, p. 410, pi. vii, figs. 25-27 (1874). 



