18 CARDIADiE. 



Cardium rusticum, Chemn. (not Linn, nor Hani.) Conch. Cab. vol. vi. pi. 19, 

 f. 197. -Mont. Test. Brit. p. 569.— Donov. Brit. Shells, 

 vol. iv. pi. 124, f. 2.— Poli, Test. Sicil. pi. 17, f. 12, 13. 

 — Lam. Anim. s. Vert. (ed. Desh.) vol. vi. p. 405. — Des- 

 hayes, Elem. Conch, pi. 25, f. 1 (good). — Philippi, Moll. 

 Sicil. vol. i. p. 52, pi. 4, f. 12, 13, 14, and vol. ii. p. 38. 



„ glaucum, Brugiere, Encycl. Method. Vers, vol. i. p. 221. — Poiret, 

 Voyage Barbarie, vol. ii. p. 13. — Wood, General Conch. 

 p. 218. — Dillw. Recent Shells, vol. i. p. 130 — Hani.. 

 Recent Shells, suppl. pi. 17, f. 36. 



„ LamarcM, Reeve, Conch. Iconica, Cardium, pi. 18, f. 93. 



„ Belticmn, Reeve, Conch. Iconica, Cardium, pi. 20, f. 113. 



„ cdule, Brown, Illust. Conch. G. B. pi. 35, f. 7.— Philippi, Moll. 

 Sicil. vol. i. p. 52, and vol. ii. p. 39. 



The contour is still more variable than in the typical 

 form, being not only irregular in the degree of elongation of 

 the posterior side, which is sometimes much produced, but 

 also exhibiting at times an obliquity which is by no means 

 constant. The valves at all stages are thinner and more 

 swollen than those of the type, and have their ribs much 

 more elevated, convex, and separated from each other by 

 broader interstices. The linear concentrically-disposed 

 scales have a great tendency to become obsolete, and are 

 usually only visible, if at all, near the front extremity and 

 towards the ventral margin, where, if present, they are 

 generally crowdedly arranged. The hinder side, and very 

 frequently the umbonal region, is stained with bluish smoke- 

 colour or livid brown, which latter tint more or less prevails 

 over the interior surface likewise. Ordinarily, but not in- 

 variably, the shape is more elongated than in the marine 

 shells, and the front, and not the hinder dorsal margin, is 

 the more elevated, so that the anterior side becomes pro- 

 portionately higher. The umbones are broad, and extraor- 

 dinarily tumid ; the ligament is decidedly smaller than in 



