296 TESTACEOUS MOLLUSCA. 
—Da Cost. t. 11, f. 6.—Crouch, t. 12, f. 8.—Cone. Man. f. 180.— 
W.t. 11, f. 74— Brit. Mol_—O. Parasttica, Turt. Dic. p. 134, f. 8; 
Biv. p. 205, t.17, f. 6, 7. Obovate, inequivalve, rounded and some- 
what dilated at the base, narrower at the apex, where, in the lower 
valve, there is a tendency to dilate and form a crest-like process at 
the sides; upper valve the less solid, very shallow, covered with 
numerous imbricated concentrically arranged loose flakes, which are 
pale ashy brown, undulated, yet scarcely raised; lower valve white, 
strong, not so shallow, armed with radiating ribs that are crossed by 
rather elevated distant concentric lamelle, which are vandyked by the 
intersection of the ribs; edges somewhat wavy, yet not at all plicated, 
neither scabrous nor crenated, but marked, for the most part, in the 
vicinity of the hinge-margin, with more or less closely disposed linear 
denticles, which run parallel to it. 4. Britain, de—Var.? O. E.? 
var. PurpuREA, Conch. Mis. O. f.8. Both valves purplish chocolate, 
not variegated, not thick; flakes of the upper valve glossy, undulated, 
very loose, not erect, those of the lower valve distant, very loose, 
curly, more or less elevated, here and there almost foliaceous ; beaks 
acute; interior slightly tinged with external colouring; cartilage 
conical; cardinal denticles indistinct. Toulon, attached to a stake. 
O. Hirreropus. Lam. 2.—Desh. E. 2, p. 288. Large, thick, round ; 
upper valve flat; the concentric lamellae very numerous and de- 
pressed. 5. Boulogne! 
O. Apriatica. Lam. 4.—Phil. in Kust. Ch. vii. 1, t. 13, f. 1, 2, 3. 
—Mid. Mal. Ros. 3, p. 6.—O. Taurtca, Kryn. Bul. Nat. Mose. 20 
(1837), t. 3, teste Mid. Subtriangular, peaked at the beaks, dilated 
below, compact, not thick, margin usually straight on one side, and 

' T have given a translation of Lamarck’s description, but, judging 
from his specimen in the Museum, consider the shell to be merely a 
coarse variety of Epuxts with the cardinal denticulations distinct and 
the lamelle of the upper valve obsolete. M. Deshayes has given the 
following more detailed account of the species :—‘ Rounded-oyal, 
thick but light, irregular, both valves covered with concentric lamelle, 
which scarcely project, and are furnished with many folds, especially 
towards the margin: lower valve larger, thicker, more tumid, and 
provided with longitudinal ribs, that are traversed by concentric scaly 
lamella: mside quite white, having slight bump-like elevations or 
undulations: scar semilunar, larger in proportion than in Epu ts, 
more laterally situated: beaks always broad and produced, that of the 
lower valve deeply hollowed by a moderately sized canal, which is 
margined on each side by a decurrent varix-like projection, that of 
the upper valve flatter, with both varices and canal nearly obsolete.” 
