192 I.J 



Manipur Molluscs. 



6ii 



Trapezoidcus dhanushori, sp. nov. 



This interesting species was found by Mr. S. L. Hora in a 

 stream known as Dhanushori at a distance of about a mile from 

 Dimapur, Assam, and is not a Manipur species. It may be 

 described as follows : — 



Shell (fig. 31) rather small, thin, trapezoidal, somewhat com- 

 pressed, with a low posterior ridge and narrow wing. Umbones 

 small, slightly tumid and deflexed inwards, sculptured with verti- 

 cal ridges radiating outwards, more marked on the two sides than 

 in the middle where they are less distinct. Anterior margin 

 obliquely truncated rounded above, sharply curved backwards 

 below; broadly rounded posteriorly. Ventral margin straight but 

 slightly curved in near the middle. Surface concentrically sculp- 

 tured with deeply impressed lines, a few radial lines are also to be 



I'Ui. 31, — Trapezoldeiis dhannsliori, Prashacl. 



A. Photograplis of the two valves of the type-shell. 



B. Minge-leeth. 



seen on the posterior region. Epidermis brownish yellow. Right 

 valve with two pseudo-cardinals, of which the outer is feebly 

 developed, and a single sHghtly arched lateral ; left valve with two 

 pseudo-cardinals, of these the inner situated under the beak and 

 continuous with the outer of the two laterals. Muscle-scars fairly 

 impressed, anterior ones separate, posterior confluent; nacre 

 greyish-yellow tinged with blue, under the beaks markedly yellow ; 

 slightly iridescent. 



Measurements of Shells (in millinietres). 



I/ength 



Breadth 

 Height 



I 



35 5 

 197 

 13-2 



34" I 

 17-3 

 11-6 



3V4 

 i8-2 



13-4 



