MARINE MOLLUSCA OF THE UNITED STATES. 175 



6. C. IsLANDicuM, Linnoeus. Figs. 451, 452, (C. pubescens). 



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

 Cardium ciliahcm, O. Fabricius, Faun. GroBnl., 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-browu, straw-colored 



within. 



Length 2.3, height 2.5 inches. 



Cape Cod, Mass., northioards. 



Cardium Hayesii and C. Daxosonii of Stimpsou are probably 

 only Arctic varieties of this species. 



Genus L.ffiVICAE,DIUM, Swainson. 

 MalacoL, 373. 1840. 



1. L. SERRATUM, Liuuseus. Fig. 453. 



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

 G. Icevigatum, Gmel., Syst. Nat., 3351. 1790. 

 C. ciirinum. 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 oblique!}' extended ; margin 

 entire or obsoletel}^ serrated ; beaks large, tumid, subcentral, con- 

 tiguous. Color very pale yellowish, covered with a very thin 

 darker epidermis, in 3'oung 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. 



