OP SOUTHERN INDIA. 151 



The figure (Jour. Am. Acad. N. Sc, Phil., 2iid ser., iii, pi. 34, fig. 18,) of the " only" 

 valve has actually very much the form of a Caryatis, and I confess myself unable 

 to see how the shell can be generically or sub-generically separated from other 

 fossil and recent Caryatis. The species is from cretaceous rocks. 

 -^j^ 2 8^. Caryatis;^ Eomer, 1862, (olim l^itar, Eom., 1857). Shell cordate or sub- 



trigonally ovate, usually of moderate thickness and somewhat inflated, white or 

 yellowish brown coloured, concentrically finely striated, pallial sinus always dis- 

 tinct, triangular or obtuse. Venus tumens, Gmelin, is the type of this very well 

 marked form of Cytherea ; its distinction from others is of great importance in 

 fossil conchology, for to it mostly appear to belong the oldest representants of the 

 genus; of recent species Pomer describes 60 and adds two doubtful ones; those 

 contained in Peeve's Monograph of Dione sadly require a revision. 



8/. JDosiniopsis, Conrad, 1864, (Proc. Ac. N. Sc, Phil., 1864, p. 213, and Am. 



Journ. of Conch., i, 1865, p. 6). Mr. Conrad (in Am. Jour, of Conch., ii, p. 100,) 



quotes among the typical species of this so-called generic form Venus plana, Sow., 



^ (=sub-plana, d'Orb.,) from the Upper Greensand of Plackdown. To judge from 



this the form of the shell does not in the least differ from typical GytlierecE, and/^-^^^ ^ j;^ ^^^ 

 neither does the hinge appear to differ. The species also occurs in our South Vk ^^^^^'^-^'^ 

 Indian cretaceous deposits, and I have examined the hin^e of this one as well as of ^^^^ ^l ''^•^^ '.^ 

 authentic Plackdown specimens. The only difference I can find is, that the lunular ' --^>-^^ «► «^ " ■ 

 tooth is rather elongated and almost parallel to the margin. Put if we compare 

 with this the hinge of other recent species, as, for instance, Cyth, [Meretrix] atte- 

 nuata of Dunker, it is evident that no reason exists for a generic or even sub- 

 generic separation. Of course, if Mr. Conrad wishes to make genera and species 

 to suit formations, and these only, he can often detect distinctions where other people 

 are unable to do so. Conrad considers _D. Meekii, which is a more rounded shell, 

 as the type species ; I do not know it, but at the same time I cannot see in what 

 to place the characters distinctive from Cytherea. 



8^. Dione, Gray, 1847, (not Megerle v. Muhlfeld, as stated by Deshayes). 

 Shell similar in form to Callista, moderately compressed, always concentrically 

 densely sulcated, and with a more or less distinct ridge running from the beaks in 

 an easy curve to the infero-posterior margin ; this ridge is sometimes provided with 

 spines; pallial sinus moderate, always distinct, usually lingui-form. The type 

 is Cyth. \_Dione'\ Veneris, Arg., C= Venus Dione, Linne). Pomer notices 

 13 species. (^cAyVhu^ylo^r- 



The so-called genus Am^ntis, &^^., which has been proposed for Cyth. callosa, A^Vj-. -^^^vJ^J 

 Con., does certainly not deserve to bear a special name. The species only differs ')-.A^^ ^Ptt 

 by having the fulcra thicker than most other species, and rugose. The general form " j^'^ ^ 



and dentition of the hinge is extremely like Cyth. [Callista'] erycina, (Linn.). ] ' ' ^ ^' 



8A. LioGoncha,M'6ii^G}i, 1853 (?). Shell roundish, sub- quadrangular or cordately 

 ovate, sometimes cuneiform, more or less inflated, solid, outer surface concentrically 



^ In adopting this name I can only repeat what I said regarding Cytherea, p. 149, (footnote). 



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