MARINE MOLLUSCA OP THE UNITED STATES. 175 



6. C. ISLANDICUM, Linnaeus. Figs. 451, 452, (C. pubescens}. 



Syst. Nat., edit. xii. 1124. 1767. 



Oardium ciliatum, O. Fabricius, Faun. Grcenl., 410. 1780. 

 Cwdium 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 UEVICARDIUM, Swainson. 

 Malacol., 373. 1840. 



1. L. SERRATUM, Linnaeus. Fig. 453. 



Syst. Nat., edit. x. 680. 1758. 

 C. Icemgatum, Gmel., Syst. Nat., 3251. 1790. 

 G. citrinum, Wood, Gen. Conch., t. 54, f. 3. 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. MORTONI, Conrad. Figs. 454-457. 



Journ. Philad. Acad., vi. 259, t. 11, f. 5-7. 1831. 



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 witli 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. 



