History of British animals - University of Guam Marine Laboratory

386 MOLLUSCA. BIVALVIA. Pecten.toothed ; convex valve gibbous, ribbed, principal costae 6, with 4 lesser onesbetween each ; surface finely transversely striated ; upper valve flat-toothed.—Sower. Min. Conch, t. lvi. f. 4-8.—In Chalk and Green Sand.3. P. aquivalvis.— Lenticular, with rounded diverging ribs, and many acuteconcentric striae ; valves equally convex, the lower one smoothest ; earsequal—Soiver. Min. Conch, t. cxxxvi. f. i.— Under Oolite.Y.Jibrosus— 4. Depressed, orbicular, with a rectangular beak, nine or tenbroadish diverging grooves, and numerous sharp concentric striae; ears equal,rectangular ; margin undulated internally—Soiver. Min. Conch, t. cxxxvi.f. 2 Under Oolite.5. P. Beaveri.— Depressed, orbicular, smooth, with irregular longitudinalcostae ; ears as wide as the shell, nearly equal.— Sower. Min. Conch, t. clviii.— Chalk Marl.6. P. orbicularis.— Orbicular, "much depressed, concentrically striated ; stria;elevated, sharp one valve smooth ears ; ; nearly equal, broadest at the base.Sower. Min. Conch, t. clxxxvi.— In Green Sand.I. P. corneus— Orbicular, much depressed, smooth ; ears small, nearlvequal; two — obtuse teeth near the ear within each valve. Sower. Min.Conch, t. cciv.— London Clay.8. P. obscurus— Suborbicular, depressed, with obscure arched longitudinalrugae upon the surface; ears large.— Sower. Min. Conch, t. ccv. f. 1.— UnderOolite.9. P. lens Orbicular, convex ;surface marked with diverging archedstriae; striae deeply punctured—Sower. Min. Conch, t. ccv. f. 2, 3— UnderOolite.10. P. laminatus.— Suborbicular, depressed, striated ; striae arched, diverging; ears triangular, unequal; the largest plaited.— Sower. Min. Conch,t. ccv. f. 4.— Under Oolite.II. P. arcuatus Orbicular, depressed, with arched, punctured, and diver.ging striae upon the surface ;ears large ;the side beneath the largest isarched.— Sower. Min. Conch, t. ccv. f. 5-7—Middle Oolite.12. P. similis.— Suborbicular, depressed, striated ; striae arched, diverging ;ears unequal ; sides straight.— Sower. Min. Conch, t. ccv. f. 6. — Under Oolite.13. Y.rigidus. — Orbicular, depressed; strongly striated ; striae arched, diverging;ears large, unequal, decussated. — Sower. Min. Conch, t. ccv. f. 8Under Oolite.14. V.barbatus Orbicular, depressed, transversely striated; rays fourteen,those upon one valve spinose; spines long, acute, depressed; earsnearlv equal.— Sower. Min. Conch, t. ccxxxi— Under Oolite.15. P. lamellosus Orbicular, convex, with concentric erect lamellae uponthe surface, and divergingstriae near the beaks ; ears large, distinct— Sower.Min. Conch, t. ccxxxix— Upper Oolite.16. P. papyraceus Depressed, obliquely oval, with large unequal rectangularears ;numerous elevated striae, decussated by the lines of growththin.— shell; Sower. Min. Conch, t. cccliv—In shale of the Coal formation.17. P. asper.— Nearly orbicular, convex on both sides, bearing about seventeensets of rays (from five to seven in each, according to the age of theshell), roughened by subtubular imbricated scales ;margin internally fimbriato-crenated; ears distinct, nearly equal— List. Conch, t. cccclxx.— Sower.Min. Conch, t. ccclxx. 1'. 1—In Green Sand.