VENERID^. 179 



GOULDTA, C. B. Ad., 1847. (Lioconcha, Morch, 1853. Thetis, 

 Ads., 1845.) Shell subtrigontil, oval, smooth, shining, inflated. 

 C. cerina. Ads. (cxxiii, 66). 



CIRCE, Schum., 1817. Shell rounded or oval ; beaks flattened ; 

 surface concentrically sculptured ; inner margin simple, or 

 sometimes crenulated ; middle cardinal teeth much stronger 

 than the others ; pallial impression trnncated, but not sinuated 

 posteriorly. G. divaricata, Chemn. (cxiii, 25). 



CRISTA, Romer, 1857. Cordate or transversely ovate, solid, 

 tumid, with radiating ribs or divaricating striae ; pallial sinus 

 very small ; internal margin crenated ; ligament in a groove, but 

 distinctly visible outside. C. pectinata, Linn, (cxiii, 26, 27). 



Subfamily MEROEIN^. 



Shell ovately elongated, moderately compressed ; hinge with 

 three or four compressed cardinal teeth, and one long lunular in 

 each valve ; the posterior margin behind the beaks is peculiarly 

 flexured and bent inside, forming a deep cavity, sometimes with 

 corrugated sides and containing the ligament hidden or almost 

 hidden ; lunule linear ; pallial sinus distinct. 



Meroi;, Schum., 1817. 



Etym. — Meroe, an island of the Nile. 



8y7i. — Cuneus (part), Megerle (not Da Costa, 1811). Sunetta, 

 Link, 1807. 



Distr. — 11 sp. Senegal, India, Japan, Australia. Fossil : 

 there are a few cretaceous and tertiary species. 3L picta, Schum. 

 (cxiii, 28). 



Shell oval, compressed ; anterior side rather longest ; hinge 

 with three cardinal teeth, and a long, narrow anterior tooth ; 

 lunule lanceolate ; ligament in a deep escutcheon. 



Grateloupia, Desmoulins, 1828. 



Distr. — Fossil, 4 sp. Eocene — Miocene ; IJnited States, 

 France. O. donaciformis, Desm. (cxv, 41). 



Shell subequilateral, rounded in front, attenuated behind ; 

 hinge with one anterior tooth, three cardinal teeth, and several 

 small posterior teeth ; pallial sinus deep, oblique. 



cytheriopsis, Conrad, 1865. "Triangular; hinge composed 

 of two compressed or linear teeth under the apex and two 

 oblique anterior to them ; in the left valve are four diverging 

 teeth, the posterior one linear, and a lateral pyramidal com- 

 pressed tooth anteriorly ; cartilage-area rugose ; pallial line with 

 a shallow rounded sinus." G. Hydana, Conr. = G. llouUnsii, 

 Lea (cxv, 29). Eocene ; Alabama. 



