OP SOUTHERN INDIA. 109 



6a. A. Adams considers the species of Theora to be Tvitliout primary teeth, 

 which certainly is not always the case. He consequently suggests for a peculiar 

 Chinese form with a "primary tooth in front of the oblique cartilage-pit" and 

 " with an internal rib extending from the beaks obliquely towards the anterior side" 

 the name Endopleum as a sub-genus. The internal rib may be characteristic, but 

 tliis is not the case as regards the presence of cardinal teeth, (see Ann. Mag. 

 Nat. Hist., xiii, 1864, p. 209). 



7. Flectodon, Carpt., 1866, (Proc. Calif. Acad. Nat. Sc, p. 207). This shell 

 is said to be allied to Necera and to have the aspect of a Theora. The shell is thin, 

 not peculiarly inflated, the upper margin is twisted under the umbones, forming 

 the cardinal tooth ; lateral teeth long, lamellar ; cartilage-pit under the umbones 

 very small, almost quite hidden, situated nest to the posterior lateral tooth ; pallia 1 

 sinus small. The species described is P. scaher from California ; the presence of 

 lateral teeth (though not sufficiently characterized) and the position of the car- 

 tilage-pit appear to indicate that the shell in question is more allied to Theora than 

 to Necera and its allies. 



8. Leptomija, A. Ad., 1864, (Ann. Mag. Nat. Hist., xiii, p. 208). "Shell 

 thin, ventricose, beaked posteriorly ; surface of valves lamellar ; hinge with an 

 oblique cartilage-pit in each valve ; right valve with two anterior primary teeth, 

 left valve with a single primary tooth; lateral teeth none; pallial sinus deep." 

 Necera cochlearis, Hinds, and Scrob. adunca, Gould, are the two species referred 

 by A. Adams to this genus. 



8«. Leiomya, A. Ad., 1864, (ibid). Shell hyaline, hinge with two prominent 

 lateral teeth; in other respects identical with ie^j^OTOya, Necera adunca, Gowldi, 

 is the type species. 



9. Fcdceomya, Zitt. and Goub., 1861, (Jour, de Conch., vol. ix, p. 194). Shell 

 in general form very much like some species of Theora, transversally elongated, 

 posteriorly somewhat attenuated and longer, anteriorly sub-truncate ; right valve 

 with two cardinal teeth separated by a cartilage groove, which is lodged very close 

 to the posterior one, one anterior cardinal tooth in the left valve ; lateral teeth 

 well developed, the posterior particularly long and the anterior rib-like. 



The form of the shell, the oblique cartilage groove, and the lateral teeth clearly 

 exhibit the great relation of this form to Theora, from which it only differs by the 

 stronger anterior lateral tooth, being rib-like, and the posterior cardinal in the 

 right valve, though the last seems to me to be identical with what I have men- 

 tioned in Theora as the thick fulcrum ; it is in some species considerably 

 thickened, especially in the right valve. The Jurassic Fal. Deshctyesi is the type 

 of the genus, and there has been, I think, only another mesozoic species described. 

 The Jurassic Corbula ? plamdata of Buvignier is also a Fcdceomya. 



10. Scrohicularia, Schuhmacher, 1817. Shell thin, rather compressed, 

 elongately broadly oval, posteriorly slightly attenuated ; hinge with one or two 

 small cardinal teeth in front of an oblique cartilage groove ; the teeth occa- 

 sionally become obsolete ; no lateral teeth. 



2d 



