394 MOLLUSCA. OSTREAD.E. Anosua. 



•• Valves plailed. 



17. O. MarshiL— Oh\ui\xc, both valves deeply plaited in seven or eight an- 

 gular diverging undulations ; edge thick, flatted — Soiver. Min. Conch, t. xlviii. 

 — Lower Oolite. 



18. O. grega/ria Clustered, oblong, curved, plaited; plaits many, rugged, 



diverging from a longitudinal plait or sulcus ; valves unequally convex ; 

 beaks produced and curved. — Sower, t. cxl. f. 1, 3. — Lower Oolite. 



19. O. palmetta. — Ovate, roundish, obscurely one-eared, depressed, with a 

 plaited mai-gin ; plaits diverging from a longitudinal space ; beaks straight.— 

 Sower. Min. Conch, t. cxl. £ 2 — Louer Oolite. 



20. O. flabelMa. — Oblong, arched ; larger valve deep, longitudinally stria- 

 ted, with a toothed margin ; the other flat and imbricated, with an entire 

 margm. (Chama plicata. Brand. Foss. f 84, 85.) Sower. Min. Conch, t. cclv. 

 — In Lo^idon Clay. 



21. O. carinata Elongated, pointed at both ends, arched ; sides flattened ; 



middle longitudinally cariniformed ; plaits numerous, angular and regular ; 



ears two, variable Mytilus Crista Galli, White, Selb. i. 12. O. car. Sower. 



Min. Conch, t. ccclxv. — In Green Sand. 



22. O. solitaria Obovate ; one valve flattish ; plaits deep, sharp, rugged, 



and branched; beaks short — Soiver. Min. Conch, t. cccclxviii. f. 1. — Found 

 near Weymouth. 



23. O. macroptcra Falciform depressed, witli a laige rectangular ear or 



wing within the curve ; margin deeply toothed ; one valve attached by a great 

 part of its surface. Sower. Min. Conch, t. cccclxviii. f. 2, 3. — Iron Sand. 



24. O. costala Orbicular ; lower valve deep, ribbed ; ribs numerous, 



branched ; upper valve flat, with an undulated margin. — Sower, Min. Conch, 

 t. cccclxviii. f. 3 — In Oolite. 



Gen. DIANCHORA. — Inequivalved ; the attached valve ha- 

 ving an 9pening in place of a beak ; the other beaked and 

 eared. 



1. D. striata. — Oblique, ovate, triangular; beak prominent ; free valve ob- 

 scurely ribbed. — Sower. Min. Conch, t. Ixxx. f. 1. — In Green Sand. 



2. D. lata. — Semicircular ; beak rising ; free valve plain Sower. Min. 



Conch, t. Ixxx. f. 2 — Mant. Suss. 205. t. xxvi. f. 21 — Podopsis striata, Cuv. 

 Oss. Foss. ii. 319. t. v. f. 2 — In Chalk. 



3. D. obliqua — Obliquely obovate ; upper valve convex, marked with nu- 

 merous diverging striae ; margin serrated — Mant. Suss. 206. t. xxv. f. 1. t. 

 xxvi. f. 12.— In Chalk. 



Gen. XCVII. ANOMIA. — Inequivalve, irregular; under 

 valve with a notch or perforation near the beak, for the 

 passage of the tendon, by which the shell adheres to foreign 

 bodies ; ligament internal, placed transversely under the 

 beak. 



389. A. electiica. — Shell somewhat orbicular, with the sur- 

 face a little undulate, transparent, and amber colour. 



