170 Records of the Ivdinn Mvseum. [Vol. XV. 



Family CORBULIDAE. 



Genus Corbula, Brugiere. 



The majority of the species of this family are marine, but a few make 

 their way up the larger rivers of South America and southern Asia into 

 water that is nearly if not quite fresh. Their range, however, never 

 extends much beyond the limits of tidal influence. The shells of these 

 brackish water forms are small, fragile and colourless, with prominent 

 single hinge-teeth. The Asiatic and American species are probably 

 convergent, but it may be convenient to group all the characteristic 

 estuarine forms under the subgeneric name Erodona, Daudin, Preston^ 

 has described several species from the delta of the Ganges. 



Corbula (Erodona) mesopotamica, sp. nov. 

 (Plate XX, figs. 12, 13.) 



Shell small, thin, inaequivalve, inaequilateral, about 1 J times as long 

 as high, rounded in front, subtruncate and produced behind, moderately 

 swollen in the central region ; umbones pointed, small, slightly pro- 

 minent, not at all introverted, situated slightly nearer the anterior 

 than the posterior extremity ; dorsal margin from umbo to upper end 

 of anterior margin slightly convex, not interrupted, from umbo to pos- 

 terior margin straight, sloping, hardly at all concave ; lower margin 

 convex, evenly curved ; surface of upper part of shell with fine irregular 

 transverse concentric striae ; striae coarser near lower margin ; no 

 sloping ridges on posterior region. The form of the hinge is shown in 

 figs. 12f/, 13a, plate XX . 



Measurements of shells {in millimetres). 



Right valve. Left valve. 



Breadth ... ... 8-5 8 



Height .... ... 5-5 .5-4 



Type specimen. — No. 11404/2M, Zoological Survey of India {Ind. 

 Mils.). 



Locality. — Nasariyeh, Mesopotamia ; subfossil in sandy beds of 

 lacustrine deposit near the Euphrates. 



The fresh shell was probably translucent, but a thin brownish epi- 

 dermis, of which traces possibly persist, may have been present. 

 The species comes nearest among described forms to C. i^fefferi, 

 Preston, from the Gangetic delta, but the shell is larger, proportionately 

 broader and more produced posteriorly ; the umbo is also more acute. 



1 Ann. Mag. Nat. Hist. (7) XIX, ]>. I'l.'") (IHOT). 



