ISOCARDIA. 473 



Werner. Soc. vol. ii. pp. 511, .535. — Born, Testacea Miis. Cses. 

 Vind. p. 80.— Chemn. Concli. Cab. vol. vii. pi. 48, f. 483.— Pom, 

 Test. Sicilise, vol. ii. p. 213, pi. 23, f. 1. 2, 3.— Dillw. Recent 

 Shells, vol. i. p. 212. — Index Testaceolog. pi. 9, Chama, f. 1. 

 Canlila cor, Bruguiere, Encyclop. Method. Vers, vol. i. p. 403. 

 Isocardia cor. Lam. Anim. s. Vert. (ed. Desh.) vol. vi. p. 445. — Turt. Dithyra 

 Brit. p. 193, pi. 14. — Flem. Brit. Anim. p. 419. — Brit. 

 Marine Conch, p. 100.— Brown, III. Conch. G. B. p. 86, p. 30, 

 f. 9, and pl. 30,* f. 5. — Sowerby, Genera Shells, Isocardia 

 f. 1, 2. — BuLWER, Zool. Journal, vol. ii. p. 258, suppl. pl. 15. 

 — Blainv. Manuel Malacologie, pl. 69, f. 2. — Crouch, In- 

 trod. Conch, pl. 8, f. 7. — Deshayes, Encycl. Method. Vers, 

 vol. ii. p. 321 ; Elem. Conch, pl. 23, f. 10, 11.— Philippi, 

 Moll. Sicil. vol. i, p. 56, and vol. ii. p. 41. — Reeve, Conch. 

 System, pl. 78, f. 1,2. — Hanl. Recent Shells, vol. i. p. 150, 

 pl. 9, Chama, f. 1 . 

 „ Hibeniica, Reeve, Conchol. Icon. Isocardia, pl. 1, f. 4. 

 Encyclop. Methodique, Vers, pl. 232. 



We are not disposed to consider the slight differences 

 which exist between the Irish and Mediterranean examples 

 of this remarkable shell, as of essential or specific import- 

 ance, but esteem them rather as contingent upon climate, 

 depth, food, or some of those multifarions causes which 

 induce variation. 



The lateral contour is exactly heart-shaped, whence its 

 popular name of the Heart Shell; the general outline of 

 each valve is cordate-truncated, the lower angle of the 

 heart being as it were lopped off by the obtuse truncation 

 of the posterior extremity. The valves are solid, opaque, 

 much inflated, and under a rather thin and yellowish- 

 brown concentrically wrinkled epidermis, of a dirty white, 

 closely reticulated by delicate angular radiatingly-arranged 

 lineations, of a livid red, or fawn-colour, which are chiefly 

 apparent (partly from the abrasion of the epidermis at that 

 point) upon the swollen umbones, behind which they be- 

 come so thickly clustered as to present an almost uniform 

 tint. The surface is devoid of either lustre or sculpture, 

 exhibiting only the more or less coarse concentric stages of 



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