OSTREIDE. 175 
often plain; lower convex, often plaited or foliaceous, and with a 
prominent beak; ligamental cavity triangular or elongated; herma- 
phrodite. 
O. edulis, Z. Reeve, Conch. lc, f 8; O. purpurea, Hanley, 
Conch. miscel. pt. 3; O. chilensts, Sowerby tn Reeves Conch. Ic., fc 33; 
O. virginica, C.M.M., not of Lamark. Ovato-orbicular, upper valve 
flat, laminated with imbricating scales; lower rugged, wrinkled ; liga- 
ment pit small, triangular; muscular impression large, lunate, scarcely 
hollowed ; purplish, white near the hinge ; interior yellowish or greenish 
white, margin purple, waved. 
Diameter about 2. 
Common. The mud oyster. Australia and Tasmania. 
Very variable in shape and color. 
O. discoidea, Gould, U.S. Ex. Ep., xii., p. 463; Reeve, Conch. Ic., 
J. 26; O. lutaria, Hutton, C.M.M., p. 84. Shell rounded, flattened, 
finely striated, whitish-brown, rayed with pale purple, sub-equivalve ; 
hinge small; lower valve convex, muscular impression very large ; upper 
valve much compressed (Sowerby). 
Pelorus Sound ; Catlin River. 
A doubtful identification; perhaps the same as the last. 
O. glomerata, Gould, U.S. Ex. Ep. xii., p. 461 ; Reeve, Conch. Ic., 
fF 52. Shell thick, irregular, sharp ribbed, with the margin dentated or 
lobed, very inequivalve ; upper valve opercular, compressed, wrinkled 
with thick concentric laminz; lower valve cucullated, purple, white 
within edged with purple or black ; lateral margins denticulated ; hinge 
generally attenuated, produced pointed (Sowerby). 
The Rock-Oyster of Auckland ; not found further south. 
O. reniformis, Sowerby ; Reeve’s Conch. Iv., f- 57. Shell thick, 
elongated, narrow, laterally arched, whitish, inequivalve ; upper valve 
compressed, flattened, a little leafy towards the margins, edged within 
with purple; lower valve deeply excavated, ventral margin straight, 
muscular impressions blackish-purple (Sowerby). 
The rock-oyster of Dunedin is referred with great doubt to this 
species. 
