888 PELECYPODA. [Eulamdlibranckia. 



KEY TO SPECIES. 



A. Margins of valves smooth inside. 



a. Shell ovato-orbicular, concentrically lamellate, left valve 



usually with short rounded ribs near the margin . . Angasi. 



/>. Shell irregular in form, left valve with concentric lamellte and 



radiating subtubular folds . . . . . . . . hi/otis. 



c. Shell suborbicular, with straight dorsal margin, free part of 

 lower valve erect in adult shells, with short rounded 

 radiate ribs . . . . . . . . . . Tntei. 



B. Margins of valves crenate within, usually only on the dorsal parts. 



a. Shell ovate, lower valve with numerous rounded radiate ribs, 



upper valve often with 3 broad purplish- black radiate 



rays . . . . . . . . . . . . corruynta. 



b. Left valve with about 6 stout bifurcating sharp ridges, mar- 



gins deeply dentated . . . . . . . . glomerata. 



c. Valves laterally arched, crescentic, concentrically lamellate . . renijormis. 



Sect. 1. OSTREA, s. str. 

 Margins of the valves smooth inside. 



1. Ostrea Angasi, Sowerby, 1871. Plate 57, iig. 3. 



Ostreo Aiujaxi, Sowerby, Conch. Icon., xviii, pi. 13, f. 27 (erroneously 

 numbered 28) ; Tate and May, P.L.S. N.S.W., xxvi, 441 ; Index, 93. 

 O. purpurea, Hanley, Conch. Misc., 1854, pi. 3 ; Angas, P.Z.S., 1867, 

 934 ; Hutton, C.M.M., 84 ; J. de Conch., xxvi, 5(3 ; Index, 93. O. lutaria, 

 Button, C.M.M., 84. O. virginica, Lamarck : Hutton. C.M.M., 84 ; 

 not of Lamarck. 0. discoidea, Uould : Hutton, J. de Conch., xxvi, 56, 

 M.N.Z.M., 175 ; not of Gould. 0. edulis, L. : Hutton, M.N.Z.M., 175 ; 

 P.L.S. N.S.W., ix, 533; not of Linne. 0. edulis Angasi, Sowerby: 

 Hutton, i.e., 533. 



Shell ovato-orbicular, slightly attached by the left valve or free, 

 greyish-brown or purple, both valves concentrically laminated, left, 

 valve usually with radiate short and rounded ribs near the margin. 

 Beaks very often produced, sharply rounded. Anterior and posterior 

 end more or less convex, the latter frequently produced. Sculpture : 

 Left valve with concentric growth-lines, generally laminate, and 

 short irregular rounded ribs toward the margin ; right (flat) valve 

 with laminated concentric scales, the radiate sculpture mostly obsolete. 

 Epidermis thick, horny, produced at the margins. Colour greyish- 

 brown to purple, the right valve often light brown and radially streaked 

 with dark purple. Interior yellowish or greenish-white, faintly shining. 

 Man/ins irregular, sharp, wavy, sometimes purple. Hinge area tri- 

 angular, elevated. Resilium triangular, winged laterally, and extending 

 over the whole of the hinge-line. Adductor -scar large, lunate, rounded 

 in front, raised and narrowed behind, not very deeply impressed, 

 situate behind the vertical median line, and very little below its centre. 

 Pallial line indistinct. 



Diameter Ant. -post., 70 mm. ; dorso-ventral, 84 mm. : thickness, 

 16 mm. 



Type in the British Museum. 



