MARINE MOLLUSCA OF THE UNITED STATES. 175 
6. C. IsuanpicuM, Linneus. Figs. 451, 452, (C. pubescens). 
Syst. Nat., edit. xii. 1124. 1767. 
Cardium ciliatum, O. Fabricius, Faun. Greenl., 410. 1780. 
Cardium pubescens, Couthouy, Bost. Journ. Nat. Hist., ii. 60, t. 3, f 6. 
(Young. ) 
Shell large and rather thin, rounded, inflated, nearly equilateral. 
Beaks prominent, incurved, contiguous; anterior dorsal area feebly 
impressed, subcordate; surface with from thirty-six to thirty-eight 
sharp ribs, which are covered with a stiff fringe-like epidermis in 
the young shells. Epidermis dull yellowish-brown, straw-colored 
within. 
Length 2.3, height 2.5 inches. 
Cape Cod, Mass., northwards. 
Cardium Hayesii and C. Dawsonii of Stimpson are probably 
only Arctic varieties of this species. 
Genus LEVICARDIUM, Swainson. 
Malacol., 373. 1840. 
1. L. sERRATUM, Linneus. Fig. 453. 
Syst. Nat., edit. x. 680. 1758. 
C. levigatum, Gmel., Syst. Nat., 3251. 1790. 
C. citrinum, Wood, Gen. Conch., t. 54, f. 8. 1817. 
Shell ovate, rather gibbous towards the umbones, smooth, shin- 
ing, anteriorly rather obsoletely striated ; whitish-yellow, posterior 
side bright citron-yellow, sometimes stained with pink towards 
the margin, yellowish within. 
North Carolina,to West Indies. 
2. L. Morront, Conrad. Figs. 454-457. 
Journ. Philad. Acad., vi. 259, t. 11, f. 5-7. 1881. 
Shell small, thin, inflated, globular, slightly oblique; surface 
smooth, posterior side somewhat obliquely extended; margin 
entire or obsoletely serrated; beaks large, tumid, subcentral, con- 
tiguous. Color very pale yellowish, covered with a very thin 
darker epidermis, in young specimens with blotches or zigzag 
lines of dark fawn color; within yellow, with generally a dark 
purple blotch along the posterior margin. 
“Length (adults) 1 inch, height 22, breadth 17 mill. 
The animal is white, has short, conical siphons, each marked 
with a circle of brown spots, and fringed with numerous cirri which 
extend far beyond the shell. 
Whole Coast. 
