Pholadomy^a. MOLLUSCA. CARDIADiE. 425 
3. P. Virata . — ^Transversely oblong, gibbose, with nine or ten longitudinal 
tuberculated ridges ; the ridge separating the shortest side the highest. — 
Sower. Min. Conch, t. cxcvii. £ 3.— Zias. 
4. P- deltoidea — Very gibbose, obtusely triangular, with eight or nine lon- 
gitudinal rugged ridges ; produced side pointed. — Sower. Min. Conch, t. cxcvii. 
£ 4. — Lias. 
5. P. margaritaeea .- — .Transversely obovate, gibbose, with an obscure lon- 
gitudinal keel, and several small ridges, concentrically undulated, pearly 
within, shortest side convex, the other slightly produced.— iS'ower, Min. Conch, 
t. ccxcvii. £ 1, 2, 3. — London Clay. 
6. Y.ficedula Transversely elongated, recurved, with numerous obliquely 
longitudinal ridges. — Sower. Min. Conch, t. ccxxv . — Inferior Oolite. 
7. P. mails — Transversely elongated, elliptical, straight, convex, with 
about nine diverging ridges.— 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.— Oolite. 
9. P. angustata — Transversely elongated, costated, gibbose ; shortest side 
rounded, the opposite compressed ; costae oblique, numerous, OLCute.— Sower. 
Min. Conch, t. cccxxvii. — Oolite. 
10. P. Murchisoni.— Ox 2 \., 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. ttCM^icosfafe.-fe^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. £ 1. (2?) — In 
Z<i«s, ib. 
12. P. cequalis. — Oval, straight ; with six or eight equal slightly elevated 
ridges over the middle. — Sower. Min. Conch, t. Dxlvi. £ 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. £ 85. 
Mya inequivalvis, Mont. Test. Brit. 38. t. xxvi. £ 7* Corbula nucleus, 
Turt. Biv. Brit. 39. t. iii. £ 8, 9, 10 — On oyster beds, common. 
Length about j%ths, breadth y%ths of an inch ; cuticle brown ; shell white, 
thick ; larger valve very convex ; smaller valve less convex ; transverse strije 
indistinct, but having a few longitudinal ridges ; inner margin obliquely flat- 
tened, and glossy. 
