TRIBE CORBULACEA. 47 



valves gibbous, smooth, and anteriorly bicarinated ; chalky white, 

 under a thin horny epidermis. 7 T¥ 9 . — Arctic Regions. 



C. Labiata. Gray. Ann. Ph. 25. — Mya L. Maton in Lin. 

 Tr. 10. t. 24. f. 4 to 7— Wood. G. C. p. 111.— W. t. 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, j. . 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. £..f. — 

 U. States. 



C. Radiata. 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. %. . Y V — 

 Acapulco. 



C. Tenuis. 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. -§-. . t 9 q. — C.America. 



C. Mediterranea. Costa. — Philippit.l.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. 



C. Biradiata. Sow. Z. P. 1833. Ovate-oblong, pale, with 

 transverse striae : dorsal edge anteriorly sub-carinated and rufous, 

 posteriorly shorter and spotted with rufous : with two intermediate 

 white rays, {inside sometimes blood red.) 2 ^ 3 . — Caraccas. 



C. Ovulata. Sow. Z. P. 1833. Ovate, whitish, sometimes 

 stained with rose colour, anteriorly sub-rostrated, posteriorly rounded 

 and somewhat produced : transversely grooved. ±±. . 1 . — S. America. 



C. Binghami.*— Sphenia B. Turt. Biv. p. 36. t. 19. /. 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. \>.\. — England. 



C. Rupicola. Desk. — Anatina R. Lam. 10. — Del. t. 3.f.4. 

 Small, pale fulvous, ovate-oblong, with external transverse grooves ; 



