MARINE MOLLUSCA OF THE UNITED STATES. 143 
parallel with the dorsal and basal margins. Greenish-olive, the 
central space faded purple. 
Length 6, height 1 inch. 
Whole Coast. 
Distinguished from £. ensis of Europe by its greater propor- 
tionate width of valves. It is altogether a more robust and larger 
species. 
Found at low-water mark, and considered excellent food. 
Genus SILIQUARIA, Schum. 
Essai, Noy. Gen., 129. 1817. 
1. S. arppa, Spengler. Fig. 332. 
(Solen.) Skrivt. Nat. Selsk., iii. 104. 1794. 
Solecurtus caribeus (Lam.) Conrad, Mar. Conch., t. 4, f. 3. 
Shell thick and solid, beaks obtuse and little elevated. Surface 
with a thick, straw-colored, concentrically wrinkled epidermis. 
Length 4, height 1.5 inches. 
Cape Cod, Mass., southwards. 
2. S. pivisA, Spengler. Fig. 333. 
(Solen.) Skrivt. Nat. Selsk., iii. 96. 1794. 
Solen fragilis, Pultney, Dorset Cat., 28, t. 4, £5. 1799. 
Solen centralis, Say, Journ. Philad. Acad., ii. 316. 1822. 
Solen bidens, Chemn. Conch. Cab., xi. 208, t. 198, f. 19389. 1795. 
Shell small and delicate, transversely oblong-ovate, compressed, 
arcuated, equilateral. Epidermis yellowish, with a purple band 
from the beaks to the basal margin. 
Length 1.5, height .5. 
Southwards from Cape Cod, Mass, 
Genus SILIQUA, Miihlfeldt. 
Entwurf. 44. 1811. 
Machera, Gould, Invert. Mass., p. 32. 1841. 
1. S. squaMa, Blainville. Fig. 335. 
(Solecurtus.) Dict. Sci. Nat., xlix. 419. 
Machera nitida, Gould, Invert. Mass., 38. 1841. 
Shell thick, oblong-ovate, beaks small; epidermis very shining, 
dark yellowish or greenish-yellow, wrinkled. 
Length 3, height 1.25 inches. 
: Northern Coast, northwards. 
2. S. costaTA, Say. Figs. 334, also 299 and 300. 
(Solen.) Journ. Philad. Acad., ii. 315. 1822. 
Shell thin and fragile, oval-oblong, much compressed, beaks 
