TRIBE MYARIA. 25 
A. Ovauis. Stutch. Z. J. 5. t. sup. 43. f. 7, 8. Inequivalve, 
thin, pellucid, posteriorly truncated : more convex valve sulcated at 
the upper edge, and receiving the inflected edge of the other valve 
which is slightly convex ; hinge with an oblique elongated internal 
cartilage. 34. 
A. Panporirormis. Stutch. Z. J. 5. t. sup. 43. f. 3, 4. 
Plano-convex, subovate, with transverse distant strize ; convex valve 
posteriorly carinated and truncated, the other valve slightly concave; 
hinge with a flat testaceous piece attached by the cartilage to the 
cardinal pits ; an indistinct depressed line obliquely crossing the 
internal disc of each valve, from the umbones to the ventral mar- 
gin. 4,9. 
A. Crassa. Stutch. Z.J.5. p.100. t. sup. 43. f.5,6. ‘Thick, 
subtriangular, inequivalve, transversely ribbed: one valve slightly 
convex, posterior side of both valves carinated, with a smooth cordate 
posterior depression. 4,,°. 
strie towards the ventral edge and anterior end, where the epidermis 
is wrinkled ; beaks prominent, inside polished, tooth broad, erect, 
little elevated, with its anterior edge fitting into the slight groove of 
a projecting plate in the opposite valve. 3..2.—U. States. 
O. Evoneata. Gray in Brit. Mus.—A Trouncatra. Lam. in 
part. Nearly thrice as broad as long, very inequivalve, beaks situated 
at 3ths the distance from the rounded posterior extremity, ventral 
and dorsal edges but little curved, subparallel in the centre ; ante- 
riorly subrostrated but truncated at the extremity, the gape very 
large ; very fragile, pellucid, the epidermis with fine radiating lines 
not visible on the dise. 4..14.— Mediterranean 
O. Brevirrons.—Lyonsia B. Sow. Z. P. 1834, Oblong, 
palish, the epidermis obscure and horny: posteriorly short and 
acuminated, anteriorly longer and attenuated ; dorsal edge anteriorly 
elongated and straightish, posteriorly short and sloping, ventral edge 
with a large elongated sloping gape at the posterior extremity. *;*. 
—W. Columbia. 
O. Picra.—Lyonst1a P. Son. Z. P. 1834. Obovate, anteriorly 
rounded, thin, anteriorly broader; the epidermis brown, painted 
with wavy black lines: dorsal edge sloping posteriorly, anteriorly 
straightish ; ventral edge with a small posterior gape, anteriorly 
rounded. 13,17.—W. Columbia. 
O. Cungeata.—Anatina C. Gray. Spic. Z. t. 3. fi 14. 
Solid, irregular, subequivalve, oblong-wedgeshaped, anteriorly pro- 
duced, posteriorly very short, subtruncated and rounded; with 
irregular concentric wrinkles, pearly within ; periostraca hard, 
greenish, extending beyond the margin ; hinge almost toothless, 
with a large moveable oblong tooth-like appendage. $..13.— 
Perit: 
