TRTBE OSTRACEA. 299 



O. Denticulata. Born, 113, t. 6, /. 9, 10 (copied E. t. 183, 

 /. 3, 4). — O. D. var. b, Lam. 15. White, inequivalve, foliaceous ; 

 upper valve the smaller, convex, subovate, glabrous; lower valve Hat 

 (being attached by the entire surface), rounded, expanded : inner edge 

 sharply toothed on both sides of the extremely broad and shining 

 cartilage in one valve, with corresponding pits in the other ; scar very 

 large, somewhat reniform. 0. China ? Judging from the figure, 

 the attached valve, when permitted to develop itself, must, as in Edulis, 

 have distant foliaceous lamina, and not improbably radiating ribs; 

 the free valve has either lost its lamella, or they are much appressed ; 

 2 or 3 marginal granules are, likewise, depicted. The 0. Denticulata 

 of Cliemnitz (f. 672, 3, copied E. 1. 183,/. 1, 2, and W. 1. 11,/. 73), and 

 of Deshayes (E. 2, p. 289) are probably distinct. 



O. Spathulata. Lam. 16. — Del. t. 17, f. 1. Oval, longitudinal, 

 dark brown or violet-black, moderately strong. Valves of equal 

 length ; the upper one shallow, covered with numerous concentric 

 rows of loose but flattened lamellae ; the lower one moderately deep, 

 with its lamellae scarcely observable, but marked with obtuse radiating 

 folds that undulate the margins. Inside white, edged in the upper 

 valve with the dark hue of the external lamellae, and sometimes in 

 the lower with dark blue : cartilage-plate rather large : cardinal den- 

 ticles large, prominent and extending nearly (if not quite) over the 

 entire periphery. 5. On mangrove branches, dc. 



O. Ruscuriana. Lam. 17. Oblong-ovate, thick (particularly the 

 lower valve), bag-shaped under the beak: inside whitish, blackish 

 purple at the margin : plate of the dorsal margin straight. " Near 

 Algiers; often pierced by Lithodomus caudigerus." I do not know 

 the species. 



O. Virginica. Gmel. 3336.— Lam. 18.— D. p. 277.— Gould, Mas. 

 p. 137.— List. t. 201, /. 34 ; t. 202, /. 35.— Fav. t. 41, /. C, 2.— E. 

 t. 179,/. 1 to b.—Sow. G.— Reeve, Sys. 1. 120,/. 2.— W. 1. 11, /. 68. 

 — D. p. 277. Elongated, narrow, nearly straight, very solid, not 

 dilated and but little rounded at the base, sides more or less sub- 

 parallel; valves rather shallow (the upper much depressed), dirty 

 white, with concentric imbricated wrinkles (covered, when not worn, 

 with crowded leaf-like scales of a dirty lead-colour) : edges not waved, 

 quite entire within ; beaks pointed, greatly produced in the adult, not 

 curved. Inside white, with the scar subcentral and usually tinged 

 with violet ; hinge as in the next species, with the successive removes 

 of the cartilage indicated in the fossule by transverse wrinkles ; callus 

 of the upper valve extending back to the apex. 12. Virginia; 

 Mexico. 



O. Canadensis. Lam. 19.— E. M. 1. 180,/ 1, 2, Z.—Ch.f. 677. 

 — O. Borealis, Gould, Mas. p. 137. — Young, O. Borealis, Lam. 3. — - 



