54 TESTACEOUS MOLLUSCA. 



white, with radiating ribs, but anteriorly smooth ; with scattered 

 concentric lamellae ; lunule distinct. t 5 q . . 1^. — Peru. 



P. Solida. Sow. Z. P. 1834. Sub-globose-elliptic, palish, 

 the umbones and the extremities brownish violet, with radiating 

 ribs but anteriorly smooth, the lines of growth sometimes sub- 

 lamellar and anteriorly more prominent. 1 . . [-^. — Peru. 



P. Discors. Sow. Z. P. 1834. Oblong-elliptic, brownish, 

 with radiating acute riblets, but anteriorly smooth ; dorsal edge 

 straight. \\ . . -J. — Peru. 



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

 whitish, with concentric riblets ; posteriorly rounded, and longitu- 

 dinally grooved ; back sloping, with a smooth lamella on one of the 

 valves : anteriorly rather acuminated, with crowded, concentric, 

 ridge-like riblets. -£o"l> — Mons. Christi. 



P. Bidentata.* Gray Ann. Phil. 25 — Mya B. Mont. t. 

 26. f. 5. p. 99. — D. p. 45. Sub-oval, compressed, dirty- white : one 

 valve with two broad flat distant diverging teeth, which project 

 forwards obliquely, the other toothless, and having only a small 

 cavity under the hinge. -J . .£. — England. 



VENERUPIS. 



Transverse, inequilateral ; posterior side short, the anterior one 

 slightly gaping ; hinge with two primary teeth in the right valve, 

 and three in the left one, and sometimes with three in each ; teeth 

 small, approximated, parallel, and slightly divergent ; ligament 

 external. 



V. Perforans.* Lam. 1.— Venus P. Mont. t. 3.f. 6.—Turt. 

 B. t. 2. /. 15 to 18. -D. p. 206.— W. t. 8. f. 108. Sub- 

 rhomboidal, margins nearly parallel, with concentric striae, forming 

 ridges at the sub-truncated anterior end, crossed by fine longitudinal 

 ones, white or brownish, with purple zigzag stripes : hinge with two 

 of the teeth cloven, syphon mark broad, and adjacent to the marginal 

 impression 1 . . 2±. rarely so large. — England, Sfc. 



V. Nucleus. Lam. 2.— Del. t. 5.f. 1. Ovate, the extremities 

 obtuse, smooth at the umbones, transversely striated ; anterior side 

 lamellar : three teeth in one valve and two in the other. ^. — 

 Rochelle. 



V. Irus. Lam. 3.— Donax I. Lin. 1128.— D. p. 156.— 

 Ch.f. 268, 9. -Don. t. 29. f. 2.—W. t. 6. /. 21. Sub-oval, 

 variable in its outline, usually truncate, margin nearly parallel and 

 straight, brownish white with elevated, concentric, distant, reflected 

 ridges and longitudinal striae in the interstices. J..f. — Mediter- 

 ranean. 



V. Exotica. Lam. A. Oval oblong, and the extremities obtuse, 



