TRIBE LITHOPIIAGI. 53 



P. Costata. 1 Gray. Ann. Phil. 25. — Venus Lapicida. Gmel. 

 3269.— D. p. 190.— Ch. f. 1664, 5.— W. t. 8./. 72. Ovate, 

 somewhat heart-shaped, whitish, protuberant at the umbones ; 

 anteriorly with longitudinal grooves, posteriorly with unequal 

 transverse striae : hinge with two teeth in one valve, a bifid one in 

 the other. 1^. — In coral in the JV. Indies. 



P. Oblonga. Sow. Z. P. 1834. Oblong-elliptic, palish, with 

 radiating riblets : anterior dorsal edge straightish, with several 

 concentric ridges which become smooth anteriorly. 7 T q 9 . — Peru. 



P. Nivea. Gray. Ann. Phil. 25.— Mytilus N. Gmel. 3358.— 

 D. p. 307. — Ch. f. 734.— W. t. 12. /. 16. Oblong, sub- 

 diaphanous, rounded at both ends, snow-white, coarsely striated 

 longitudinally, and the margin acute : within, glossy white, f . . If . 

 — Nicobar Islands. 



P. Dactylus. Sow. G. f. 3.— Gould, p. 65. f. 41. — Reeve. 

 t. 51. f. 3. Transversely elongated, very convex, rounded at both 

 ends, concentrically wrinkled, and longitudinally ribbed at the 

 short posterior extremity : white, the ventral margin rounded, the 

 umbones tumid, and the anterior side very long : teeth, two in one 

 valve, three in the other. f- . . 1^. — N. America. — Bears a close 

 resemblance to Chemnitz* s figure of Nivea , but the localities are so 

 widely apart as to sanction their separation. 



P. Rugosa. Sow. Z. P. 1834. Oblong, pholas-shaped, whitish, 

 with radiating riblets of very fine concentric striae ; the margins 

 usually deformed. ^ . . If. — Chili. 



P. Denticulata. Sow. Z. P. 1834. Oblong, pholas-shaped, 

 palish, but internally stained with blackish brown on the ex- 

 tremities : posteriorly sub-rostrated, anteriorly rounded ; dorsal 

 edge nearly straight, ventral edge rather prominent : entirely 

 covered with radiating grooves and concentric striae, which pos- 

 teriorly are sub-lamellar and denticulated. f.-l T 3 o- — Peru. — 

 Variety, shorter, and none of the striae sub-lamellar or denticu- 

 lated.— isfe of Plata. 



P. Tenuis. Sow. Z. P. 1834. Oblong, pholas-shaped, whitish, 

 thin ; with radiating riblets, which are stronger at the sides and 

 are decussated by rugulose very fine striae ; posterior side very 

 short, ii.; 1. — Peru. 



P. Amygdalina. Sow. Z. P. 1834. Thin, sub-hyaline, yel- 

 lowish, obovate, smooth ; posterior side very smooth and narrower ; 

 anterior longer, broader, with some distant raised lamellae. ^ . . 1 t 3 q. 

 — Gallapagos. 



P. Elliptica. Sow. Z. P. 1834. Ovate-elliptic, reddish 



1 P. Linguatula, Lam. 13, bears so close a resemblance to 

 Saxicava Rugosa as scarcely to deserve separation. 



