184 CYRENIDA. 
( Cyrenacea.) 
Famity CYRENIDA. 
Shell suborbicular, closed, ligament external; epidermis thick, 
horny ; umbones of aged shells eroded; hinge with two or three 
cardinals and lateral teeth; pallial line with a small inflection. 
Animal with mantle open in front, margins plain; siphons 
(1 or 2) more or less united, orifices usually plain; gills two on 
each side, large, unequal, united posteriorly ; palpi lanceolate ; 
foot large, tongue-shaped. 
Mr. Temple Prime, who has made a special study of this 
family, asserts that Oriental species of Cyrena and Corbicula 
differ from the American in not having a pallial sinus, but Dr. 
Stoliczka has observed it in Asiatic species, although not so 
well-developed as in those inhabiting America; it is present, but 
shallow, in fossil species of the Paris Basin. 
bs 
Cyrena, Lam., 1806. 
Etym.— Cyrene, a nymph. 
Syn.—Pseudocyrena, Bourg., 1856. Cyanocyclas, Fer., 1818. 
Cyrenocyelas, Agass., 1847. Polymesoda, Raf., 1820. Lepto- 
siphon and Cyrenocapsa, Fischer. Miodon, Ditypodon, Loxop- 
.tychodon and Donacopsis, Sandberger. 
Distr.—100 sp. South America, Southern United States, 
East Indies, Polynesia. Fossil. Cretaceous—; North America, 
Kurope. C. Cyprinoides, Quoy (exiv, 38). 
Shell rather thick, inflated or a little compressed, rounded or 
subtrigonal, subinequilateral, close, covered with a thick, greenish 
epidermis; three subequal, divergent, cardinal teeth in each 
valve; lateral teeth two, smooth or striated, the anterior rather 
thick, short, close, the posterior sublamellar, distant; beaks 
contiguous, eroded; ligament long and swollen; margins simple; 
muscular impressions small, oblong; pallial sinus inconspicuous. 
Animal with the mantle open in front and below, margins 
plain; siphons short, orifices fringed; gills unequal, square in 
front, plaited, inner lamina free at base; palpi lanceolate ; foot 
strong, tongue-shaped. 
Cyrena inhabits the brackish waters of warm countries; they 
are usually found near the coast, often buried in the mud of 
mangrove-swamps. CC. Carolinensis, Bosc, occurs plentifully in 
the rivers and swamps of So. Carolina, Georgia and Florida. 
EGETA, H. and A. Adams, 1857. (Anomala, Desh.) Shell 
ventricose, thin, anteriorly short, posteriorly longer,subrostrated. 
C. Floridana, Conr. (exv, 31). 
piopus, Gabb, 1868. (Cyprinella, Gabb, olim.) Shell equi- 
valve, subecordiform; hinge with three diverging (simple?) car- 
dinal teeth, and one anterior and one posterior lateral smooth 
