504 Records of the Indian Museuvi- [Voi.. XXII, 



distinct sculpture of rather thick wavy h'nes ; they show distinct 

 V-shaped curvatures in the upper regions of the umbones, and 

 some of the lines extend on to the posterior wing as well. The 

 posterior ridge is not single but distinctly double, and in some 

 specimens another faint ridge is also indicated above the^e ridges. 

 In outline, as stated above, the specimens quite resemble Drouet 

 and Chaper's figures. The specimens are all quite fresh, and are 

 of a brownish yellow colour with a few greenish stripes in the 

 region of the posterior wing. The largest specimen does not 

 exceed 40 mm. in length. 



This form had hitherto been known from Borneo only but the 

 forma typica and other nearly allied forms have been recorded 

 from Sumatra. 



The animal resembles that of the .species C. hageni and C. ver- 

 hecki described by Haas [loc. cit., pp. 175, 199 and 200, text- 

 figures 2, 3). 



Family Cyrenidae. 



Genus Cyrcna (Lam.) Gray. 



Cyretaa sumatrensis, Sowerby. 



1897. Cyreiia mniatrensis, v. Martens, op. cjf., p. 92. 



One complete specimen and a few rather worn shells of this 

 species were collected from the mangrove-swamps at Belawan 

 (Deli). These specimens agree fairly well with the large series of 

 this species in the Indian Museum collection. 



Genus Corbicula, Meg. 



In Mr. den Doop'sSumatran collection the genus is represent- 

 ed by dry shells of the four species dealt with below, and a few 

 young shells which it is not possible to identify specifically. It 

 may also be noted here that the shells of practically all the speci- 

 mens are greatly eroded. 



Corbicula moltkeana, Prime. 



1897. Corbicula moltkeana, v. Martens, op.cit.. pp. Ill, II2. 



This species is represented by a few rather imperfect speci- 

 mens from a streamlet at Timbang Langkat. The specimens 

 closely agree with a specimen named by the late Prof. E. von 

 Martens. 



Corbicula trapezoidea, v. Martens. 



1897. Corbicula trapezoidea. w Martens, op.cit.. pp.115. "''■ pl- v". 

 figs. 14-19. 



A. single specimen from .a streamlet at Timbang Langkat 

 agrees in shape and hinge-teeth with one of v. Martens' co-types, 

 but the ribs on the surface are more closely situated and not so 

 prominent as in that specimen. 



