142 Records of the Indian Museum. [Vol. XXII . 



Cyrena tennentii, Hanley. 



Plate XX, fig. 10. 



1858. Cyrena tennentii, Hanley, Proc.Zool. Soc. London XX\'I, p. 2.^. 



1869. Cyyena tennentii, Prime, Amer. Journ. Conch. \ , p. 148. 



1879. Cyrena tennentii, Clessin. Cycladeen in Martini-Chemn. Condi. 



Cab., p. 240. 

 1915. Cyrena tennentii. Preston, Fnini. Brit. Ind. Fresli'dK-MoU ., 



p. 206. 



The two specimens from Ceylon, which I assign to this 

 species, agree fairly well with Hanley's description except that the 

 shells of both these specimens, owing to the greatly arcuate ventral 

 border, have become suborbicular instead of being ovato-subtii- 

 gonal. This might partly be due to age as the larger of my 

 specimens is much larger than Hanley's, while both the specimens 

 are much deeper. I figure the larger of the two specimens and 

 give below the measurements. 



Measurements (in millimetres). 

 Length 

 Height 

 Thickness 



Habitat. — The species is only known from Ceylon. Hanley's 

 specimens were taken in the Ariho River flowing into the Gulf 

 of Manaar, but the exact locality of the specimens in the Indian 

 Museum is not stated. It seems to be rather scarce in Ceylon 

 also, as in the large collections made in the island by the late 

 Mr. G. Nevill no specimens of the species are present. 



Remarks. — The shell of this species is comparatively thinner 

 and shorter than that of the other Indian species of the genus. 

 The hinge is comparativeh' broad and greatly curved, theumbones 

 are small but prominent, recurved anteriorly and inwards and 

 nearly approximating with each other in the maddle line. The 

 shape of the shell and the position of the umbones is very char- 

 acteristic of this species and easily distinguishes it from all other 

 Indian forms. 



Cyrena ceylonlca (Chemnitz). 

 Plate XX, figs. II— 13. 



'9'S- Cyrena ceylonica, Preston, Faiin. Brit. hid. Freslnn.-MoU ., 

 p. 202. 



Preston's work cited above gives all references to literature, 

 but the description of the species taken from Sowerby's Concho- 

 logia Iconica is very inadequate, nor is there any other complete 

 account of the shell available. I have, therefore, thought it 

 desirable to give a detailed description. 



Shell very large, solid, oblong-ovate or even sub-rhomboidal, 

 somewhat compressed, very high, markedly inequilateral ; covered 

 with a thin dark yellowish to brownish or even black epidermis 

 with thin fringed striae ; regions of growth marked as coarser and 



