TRIBE CARDIACEAr. 143 



C. Cardissa. Lin. 1121.— Z). p. WO.— Lam. 45.— Cli. f. 

 143, 4.— W. t. 5. /. 53.— ii". t. 293. /. 3. (Yoio^c/. C. Dio- 

 NEUM, C.I.f. 1.) Heart-shaped, with the valves compressed but 

 convex on both sides, white, thin, with the ribs granulated, (the 

 posterior ones being the more prominent), the keel toothed and 

 the umbones appi'oximated, with a small cordiform depression under 

 them ; the anterior side convex near the hinge, becoming flattish 

 towards the margin. — From keel to keel, 2\. — Indian Ocean. 



C. MoNSTRosuM. Chem. f. 149, \bO.— Gmel 3253.— i>. p. 

 112. — C. Inversum. Lam. AQ. — E. t. 295. f. 1. Heart-shaped 

 with the valves compressed, the anterior side convex and 

 lightly grooved, the posterior concave with subgranular ribs, and 

 the lower extremity of the valves curled up towards the beaks ; 

 white with yellowish spots and chevrons disposed the whole length 

 of the keel, which is armed with very small distant points : um- 

 bones approximated From heel to keel 1^. — Nicobar Isles. 



C. HuMANUM. Chem. f. 145, d.-D. p. 111.— TF. t. 5./. 

 54.— C. JuNONi,E. Lam! 47.— E. t. 294. f. 20. Heart-shaped, 

 the valves compressed, and the keel nearly unarmed ; purplish red 

 or white with rosy spots, the anterior side concave and lightly 

 grooved, the posterior ribbed and somewhat granular : umbones 

 approximated. — Variety. Ch.f. 147,8. — C. Roseum. D.p.\\2. 

 — Variety. E. t. 294. f. 2.— From keel to keel, 2.— Indian 

 Ocean. 



C. LiNEATUM. Lam. 4^. — C.I.f. 23. Heart-shaped, keeled, 

 obliquely truncated anteriorly, very glabrous, thin, rayed with 

 white and fulvous, with transverse undulating striee ; within reddish 

 near the beaks and indications of ribs towards the margin. 1 . — 

 America. 



C. Imbricatum. Sor\ Jun. Z. P. 1840.— C. If. 48. Thick, 

 ventricose, rounded posteriorly, anteriorly subquadrangidar and 

 angulated, white within, oi'ange with purple spots ; the twenty-eight 

 ribs, (of which the nineteen posterior are strongly imbricated, the 

 extreme anterior subangulated and smoothish,) are angulated and 

 rough with vaulted imbrications near the umbones, near the ventral 

 margin obtuse, \-f\j' • H* — Swan River. — Like JMedinvi in shape. 



C. FoRNicATUM. Sow. Jun. Z. P. \M0.— C. If 50. Sub- 

 quadrangular, angulated anteriorly, rounded posteriorly, white with 

 purple spots ; within orange spotted with reddish purple at the 

 margins : with thirty-five ribs, the twenty-three posterior ones 

 biangulated, imbricated with most minute pointed crenulations at 

 the sides. 1. . 1. — Like Bledlnm in shape. 



C. BlANGULATUM. Brod. .J" Sow. Z. f 4. — C. I. f. 2.— 

 Reeve, t. 73. f. 2.— Beech. Zool. t. 42./. 5.— C. If 2. Turgid, 

 obliquely subcordate, anteriorly biangulated, posteriorly rounded ; 

 marbled with whitish, greyish, purple, and chesnut ; the radiating 



