VENERIDZ. 179 
aoutpra, ©. B. Ad., 1847. (Lioconcha, Moérch, 1853. Thetis, 
Ads., 1845.) Shell subtrigonal, oval, smooth, shining, inflated. 
C. cerina, Ads. (exxiii, 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 truncated, but not sinuated 
posteriorly. C. divaricata, Chemn. (exiii, 25). 
crisTA, Rimer, 1857. Cordate or transversely ovate, solid, 
tumid, with radiating ribs or divaricating striz; pallial sinus 
very small; internal margin crenated ; ligament in a groove, but 
distinctly visible outside. C. pectinata, Linn. (exiii, 26, 27). 
Supramity ME ROKINA. 
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. 
Merok, Schum., 1817. 
EHtym.—Meroé, an island of the Nile. 
Syn.—Cuneus (part), Megerle (not Da Costa,1811). Sunetta, 
Link, 1807. 
Distr.—l11 sp. Senegal, India, Japan, Australia. Fossil: 
there are a few cretaceous and tertiary species. M. picta, Schum. 
(exili, 28). 
Shell oval, compressed ; anterior side rather longest; hinge 
with three cardinal teeth, and a long, narrow anterior tooth; 
5) 
lunule lanceolate ; ligament in a deep escutcheon. 
GRATELOUPIA, Desmoulins, 1828. 
Distr.—Fossil, 4 sp. Hocene—Miocene; United States, 
France. G. donaciformis, Desm. (exy, 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. Moulinsii, 
Lea (cxv, 29). Eocene; Alabama. 
