54 TESTACEOUS MOLLTJSCA. 



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

 concentric lamellae ; lunula distinct. -j% . . 1^. — Peru. 



P. SoLiDA. Som. Z. P. 1834. Sub-globose-elliptic, pahsh, 

 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 . . ly\. — Peru. 



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

 with radiating acute riblets, but anteriorly smooth; dorsal edge 

 straight. \\ . . -i. — Peru. 



P. CoNciNNA. 8oTK.. 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. -gV"! — Mons. Christi. 



P. BiDENTATA.* Gray Ann. Phil. 25 Mya B. Mont. t. 



26./. 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, l . .4. — • 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 

 externa). 



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

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

 rhomboidal, margins nearly parallel, with concentric strise, 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. \..2\. rarely so large — England, 8fC. 



V. Nucleus. Lam. 2. — Del. t. b.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. J. — 

 RocheUe. 



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

 Ch. f. 268, ^. — Don. t.29.f. 2.—W. t. 6. f. 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, h-'i- — Mediter- 

 ranean. 



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



