Pholadomyj5a. MOLLUSCA. CARDIAD^. 425 



3. P. lirata.— Transversely oblong, gibbose, with nine or ten longitudinal 

 tuberculated ridges ; the ridge separating the shortest side the highest. — 

 Sower. Min. Conch, t. cxcvii. f. 3 — Lias. 



4. P. deltoidea Very gibbose, obtusely triangular, with eight or nine Ion- 



oitudinal rugged ridges ; produced side pointed. — Soiver. Min. Conch, t. cxcvii. 

 i. 4 Lias. 



b. P. margaritacea. — Transversely obovate, gibbose, with an obscure lon- 

 gitudinal keel, and several small ridges, concentrically undulated, pearly 

 within, shortest side convex, the other slightly produced. — Soiver. Min. Conch. 

 t. ccxcvii. £ 1,2, 3 — London Clay. 



6. V.ficedula Transversely elongated, recurved, with numerous obliquely 



longitudinal ridges. — Soiver. Min. Conch, t. ccxxv. — Inferior Oolite. 



7. P. ovalis Transversely elongated, elliptical, straight, convex, with 



about nine diverging ridges. — Sower. Min. Conch, t. ccxxvi — Upper Oolite. 



8. P. ambigua Transversely elongated, gibbose, slightly recurved, ante- 

 riorly ? gaping, with several oblique diverging ridges — Sower. Min. Conch. 

 t. ccxcvii. — Inferior Oolite. 



9. P. angustata Transversely elongated, costated, gibbose ; shortest side 



rounded, the opposite compressed ; costse oblique, numerous, acute.— Sower. 

 Min. Conch, t. cccxxvii. — Oolite. 



10. P. Murchisoni.— Oval, with large beaks, the anterior side short, six or 

 seven prominent obtuse, knotted ribs ornament the middle — Sower. Min. 

 Conch, t. Dxlv — In Lias at Brora. 



11. P. aculicostata.— Oval, elongated, with four or five large keel-shaped 

 ribs upon the very short anterior side, and many gradually lessening ones 

 over the middle of the shell, — Sower. Min. Conch, t. Dxlvi. f. 1. (2?)— In 

 Lias, ib. 



12. P. aqualis. — Oval, straight ; with six or eight equal slightly elevated 

 rido-es over the middle. — Sower. Min. Conch, t. Dslvi. f. 3 — Oolite. 



CORBULADiE. 



Gen. CXI. CORBULA. — Shell triangular ; hinge with a sin- 

 gle conical tooth, and adjacent hollow in one valve, and a 

 spoon-shaped tooth, and hollow in the other. 



— 443.- C. striata. — Beaks gibbous, strongly striated trans- 

 versely. 



Cardium striatum apicibus reflexis, Walk. Test. Min. 24. t. iii. f. 85. 

 Mya inequivalvis, Mont. Test. Brit. 38. t. xxvi. f. 7- Corbula nucleus, 

 Turl. Biv. Brit. 39. t. iii. f. 8, 9, 10. — On oyster beds, common. 



Length about T 4 5 ths, breadth / 5 ths of an inch ; cuticle brown ; shell white, 

 thick ; larger valve very convex ; smaller valve less convex ; transverse striae 

 indistinct, but having a few longitudinal ridges ; inner margin obliquely flat- 

 tened, and glossy. 



