TRIBE CORBULACEA. 47 
valves gibbous, smooth, and anteriorly bicarinated ; chalky white, 
under a thin horny epidermis. +,,2.—Arctic Regions. 
C. Lasrata. Gray. Ann. Ph. 25.—Mya L. Maton in Lin. 
Tr. 10. t. 24. f. 4 to 7.— Wood. G. C. p. 111.—W. ¢. 3. f. 39. 
Sub-triangular, sub-equilateral, thick, nearly smooth, moderately 
convex, rounded at both ends ; white under an olivaceous epidermis, 
the ventral edge simple and somewhat arcuated, the more convex 
valve greatly lapping the other. ?..1.—S. America. 
C. Contracta. Say. Jour. A. N. S. Phil. 2. p. 312.— 
Gould. Mas. p. 43. f. 37. Sub-ovate, sub-equivalve, ventricose, 
white, with regular strong smooth rounded transverse ridges: beaks 
not prominent, sub-central ; posteriorly rounded, anteriorly narrowed 
and sub-acute ; ventral edge incurved near the middle, and one 
half of the edge of one valve concealing that of the other. 4..2.— 
U. States. 
C. Raprata. Sow. Z. P. 1833. Sub-trapeziform, whitish, 
rayed with blood red near the ventral margin : posterior side short, 
anterior longer and doubly keeled: inside blood red. 4..3.— 
Acapulco. 
C. Tenuts. Sow. Z. P. 1833. Oblong, whitish, thin; the 
anterior side the longer, with two keels, anteriorly biangulated ; the 
posterior side sloping dorsally, posteriorly rounded: anterior edge 
sloping ; the umbones sub-incurved : anterior dorsal edge sub-exca- 
vated. 3..-9,.—C. America. 
C. MepiterraANgEA. Costa.—Philippit.1.f. 18. Minute, ob- 
long, equilateral sub-triangular, compressed, glossy, thin, smoothish, 
yellowish, with usually three darker rays : hinge of the larger valve 
with two teeth, one bifid and larger, a single denticle in the other. 
1,.34.—Sicily. 
C. Brrapiata. Sow. Z, P. 1833. Ovate-oblong, pale, with 
transverse striz : dorsal edge anteriorly sub-carinated and rufous, 
posteriorly shorter and spotted with rufous: with two intermediate 
white rays, (inside sometimes blood red.) *33.—Caraccas. 
C. Ovuntata. Sow. Z P. 1833. Ovate, whitish, sometimes 
stained with rose colour, anteriorly sub-rostrated, posteriorly rounded 
and somewhat produced: transversely grooved. 44..1.—S. America. 
C. Bincuami.*—Spuenia B. Turt. Biv. p. 36. t. 19. f. 3. 
Inequivalve inequilateral, open, anteriorly wedge-shaped, posteriorly 
truncated ; cuticle brown, wrinkled : beaks rather prominent, with 
the points not quite opposite but divaricating from each other : 
hinge in one valve, with an elevated transversely dilated tooth run- 
ning in a gradually narrower and wedge-shaped manner nearly half 
way along the hinge margin ; a concave tooth and small denticle 
before it in the other. 4..3.— England. 
C. Rurrcora. Desh —Anatina R. Lam. 10.—Del. t. 3. f. 4. 
Small, pale fulvous, ovate-oblong, with external transverse grooves ; 

