184 CYRENIDiE. 



( Cyrenacea.) 

 Family CYRENID^. 



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 stud}^ 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. 



Cyrena, Lam., 1806. 



Etym. — Gyrene^ a nymph. 



Syn. — Pseudocyrena, Bourg., 1856. Cyanocyclas, Fer., 1818. 

 Cyrenocyclas, Agass,, 1841. Polymesoda, Raf., 1820. Lepto- 

 siphon and Cyrenocapsa, Fischer. Miodon, Ditypodon, Loxop- 

 tychodon and Donacopsis, Sandberger. 



Dii<tr. — 100 sp. South America, Southern United States, 

 East Indies, Polynesia. Fossil. Cretaceous — ; North America, 

 Europe. G. GyprinoideH^ Qi-^oy (cxiv, 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 

 A'alve ; 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 usiially found near the coast, often buried in the mud of 

 mangrove-swamps. G. Ga7-oHnensis, 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. 

 G. Floridana, Conr. (cxv, 31). 



DIODUS, Gabb, 1868. (Cyprinella, Gabb, olim.) Shell equi- 

 valve, subcordiform ; hinge with three diverging (simple?) car- 

 dinal teeth, and one anterior and one posterior lateral smooth 



