138 CORBULTD^. 



Shell equivalve, globular or suboval, very inequilateral, widely 

 gaping posteriori}' ; a spoon-shaped process and small cardinal 

 tooth in each valve; ligament double, external and internal; 

 ]>allial impression very short and simply arcuated. 



Siphon ver}^ short, truncated, scarcely extending beyond the 

 valves. Lives in indurated clay at the mouths of rivers, in 

 Senegal. 



Family CORBrLIDJE. 



Shell small, inequivalve, thick, gaping in front ; hinge con- 

 sisting of a single recurved tooth in one valve, received into a 

 fosset or notch in the other. 



Animal uns^^mmetrical ; mantle closed except in front, the 

 narrow opening dentate ; siphons united, short, fringed. Living 

 in the sand or mud on the seashore or in estuaries, 



CoRBULA, Bruguifere. 



Etyvfi. — Corbula, a little basket. 



Syn. — Erodina, Daud. (^ Pacyodon, Beck.) Agina, Turt. 



Dist?\ — 73 sp. United States, Norway, Britain, Mediterranean, 

 West Africa, China. Inhabits sandy bottoms; lower laminarian 

 zone — 80 fathoms. Fossil, 120 sp. Inferior Oolite — ; Europe, 

 India. Laramie — ; United States. C. Mediterranea, Costa, {cv^ 

 93\ C. sulcata, Brug. (cv, 94). 



Shell thick, inequivalve, gibbose, closed, produced posteriorly; 

 right valve with a prominent tooth in front of the cartilage-pit ; 

 left valve smaller, with a projecting cartilage-process ; pallial 

 sinus slight ; pedal scars distinct from the adductor impressions. 



Animal with very short, united siphons ; orifices fringed ; anal 

 valve tubular ; foot thick and pointed ; palpi moderate ; gills 

 two on each side, obscurel}^ striated, 



T^NiODON, Dunker, 1851. Shell ovately elongated, subequi- 

 lateral, smooth, equivalve, and apparently closed, right valve 

 with a cardinal tooth under the umbo extending forwards, left 

 valve with a distinct marginal cartilage-pit behind the beak. 

 Type, T. ellipticus, from liassic beds near Halberstadt (German}^;. 

 The ligament was partially external, partly internal, the valves 

 not gaping. 



ANisoRHYNCHUS, Conrad. Shell nearly or quite equivalve, 

 transversely p3a'iform, the posterior side being rostrate ; beaks 

 nearly equal, and distinctly incurved. Hinge, muscular and 

 pallial impressions as in Corbula, except that the cardinal tooth 

 is furrowed. 



C. pyriformis, Meek. Associated with fresh- and brackish- 

 water types. 



PACHYODON, Gabb, 1868, (Anisothyris, Conr.) F. oMiqua, 

 Gabb (cvii, 33-35). Associated with marine and estuary types. 



