136 VENERIDiE. 



have been worn off, leaving the surface nearly smooth ; there are no 

 conspicuous radiating lines upon the beaks forming a lattice-work 

 with the concentric ridges ; but between the ridges are fine lines of 

 growth. The surface is shining, not chalky, of a flesh-color, and with 

 zigzag blotches of fawn-color or brown ; these, however, arc not always 

 present. The interior is wholly of a yellowish white. The lower 

 outline of the figure shows its form compared with V. mercenaria. 



Venus prcrparca seems to me to be the same thing, in which merely 

 the zigzag lines are wanting. Lives along the shores of Cape Cod. 



Oenns TAPES, Muhlfeldt. 1811. 



Shell triangular or rhomboidal, rather solid, grooved concen- 

 trically but not deeply ; lunule lanceolate or indistinct ; teeth, three 

 cardinals, which are erect and slender, and an oliscurc lateral (as 

 in the other genera) in each valve ; inside margin plain. Body 

 oval or oblong ; mantle having its edges plain ; tubes more or less 

 united ; foot usually furnished with a byssal groove. 



Tapes fluctuosa. 



Fig. 50. 



Shell transversely ovate, lenticular, Avliite, with a yellowish epidermis; sur- 

 face Avith recurved, concentric waves vanishing at the sides ; areola none, or in- 

 distinct in old specimens. 



Fenus fluctuosa, Gould, Inv. Mass. 1st ed. 87. — De Kay, Nat. Hist. New York, 220. — 

 Gr.\y, Cat. Brit. Mus. (Biv.) 176. — Reeve, Conch. Icon. pi. 24, fig. 1196. 



Tupes fluctuosa, Deshates, Cat. Br. Mus. (Biv.) 176; non T. f. — Sowerby, Thes. pi. 

 163, fig. 16.3. 



Venus astiirtoidcs. Beck (1849), in Middend. Beitr z. c. Mall. Ross. iii. 56; Siber. 

 Reise, 92 (1851), pi. 20, figs. 7-13. — Sowerby, Tlics. ii. 737, pi. 138, fig. 157. 



Shell oblong-ovate, lenticular, rather thin, nearly equipartite ; 

 white, beneath a glossy, thin, straw-colored epidermis ; anterior part 

 shortest and broadest ; both ends widely rounded ; beaks 

 ^'^ '' slightly elevated, with a smooth, heart-shaped space before 

 them, not distinctly defined by any boundary ; surface with 

 from twenty to twenty-five concentric waves, not quite ex- 

 . fluctuosa. ^gjj^jjj^g ^Q ^|j(, margin, especially anteriorly, so that the 

 marginal edges arc plain ; when closely examined, these waves or 

 ridges are found to be compressed, thin, and inclined towards the 

 beaks ; cardinal teeth three in each valve, the middle one cleft in 

 both valves ; muscular and pallial impressions very superficial, the 



