OP SOUTHERN INDIA. 261 



a special family for it which they place near to the Cyrenid^, but the form of the 

 hinge, that of the muscular impressions, and the peculiar silky structure of the internal 

 shell, possessing at the same time a certain amount of roughness, so characteristic 

 for the TJnqulinidm leaves, I think, very little doubt that the true ally of 

 Cyrenoida is Mysia ( — DiplodontaJ ^ and not Cyrena. With the last it has actually 

 only the outer rough epidermis in common, but this also occurs in JJngulina^ as well 

 as in most of the brackish- water or estuary shells. 



5. Felania, Hecluz, 1851. Shell roundish, compressed, or somettmes ovately 

 elongated, thin, covered with a smooth, finely striated shining epidermis, hinge with 

 two diverging cardinal teeth in each valve, the anterior in the left and the posterior 

 in the right being bifid ; muscular impressions large, oval ; pallial line truncate 

 posteriorly or with a very short sinus. Type, FeL diaphana, Gmel., (le Falun of 

 Adanson, — Lucina Adansoni, Heeve,) from the Senegal. Reeve in his monograph 

 of Lucina describes several other species chiefly from Central America. A few 

 species also occur in the estuaries along the coast of the Bay of Bengal ; they 

 appear to be as yet undescribed. In two of our eastern species I have not observed 

 any posterior sinus, the pallial impression being distinctly entire, slightly truncate 

 posteriorly ; the muscular scars are marginal, elongated, and flexuous. 



6. J/y6^m, Leach, 1827, [P1820] C=I)iplodonta, Bronn, 1831). Shell sub- 

 orbicular or roundly quadrangular, more or less tumid, concentrically striated, hinge 

 with two cardinal teeth in each valve, the anterior in the left and the posterior in 

 the right being bifid, but the teeth of the left are generally smaller and the ante- 

 rior has sometimes the front half obsolete ; internal hinge margins in front and 

 behind the beaks usually slightly channelled, muscular impressions elongated, 

 sub-marginal, pallial line entire; type, Mysia rohindata, Mont. 



It having been ascertained that the Tellina rokmdata of Montagu was selected 

 by Leach as the type of his genus, there is no reasonable ground to be given 

 upon which the priority of Bronn' s Diplodonta could be based. I am not aware 

 that Leach's name was published in 1820, but it certainly was used in 1827 by 

 Brown in his Conchol. Illustrations for the type species M. rotundata, and as this 

 shell must have at that time been well known through the researches of Montagu, 

 Dillwyn, Wood, Turton, and others, its generic priority against that of Diplo- 

 donta cannot be ignored. Mysia differs from Felania by a somewhat more solid 

 structure of the shell, want of an olivaceous epidermis, perfectly entire pallial 

 impression, and somewhat more elongated muscular scars. Species of Mysia are 

 rare in cretaceous deposits, and their occurrence in still older rocks is doubtful. 



7. Fsathura, Desh., 1860, (Paris foss., 2nd edit., i, p. 478). Shell elongately 

 ovate, thin, resembling Clementia, each valve with two diverging cardinal teeth, 

 those in the right are both bifid, in the left only the anterior is bifid ; muscular 

 impressions narrow, marginal, elongated, pallial line entire. Type, Fs. fragilis^ 

 Desh., from eocene beds of the Paris basin. 



