386 
MOLLUSCA. BIVALVIA. 
Pecten. 
toothed ; convex valve gibbous, ribbed, principal costae 6, with 4 lesser ones 
between each ; surface finely transversely striated ; upper valve flat-toothed. 
— Sower. Min. Conch, t. Ivi. f. 4-8. — In Chalk and Green Sand. 
3. P. cequivalvis. — Lenticular, with rounded diverging ribs, and many acute 
concentric striae ; valves equally convex, the lower one smoothest ; ears 
equal Sower. Min. Conch, t. cxxxvi. f. i. — Under Oolite. 
4. P. fibrosus — Depressed, orbicular, with a rectangular beak, nine or ten 
broadish diverging grooves, and numerous sharp concentric striae; ears equal, 
rectangular ; margin undulated internally, — Sower. Min. Conch, t. cxxxvi. 
f. 2 — Under Oolite. 
5. P. Beaveri. — Depressed, orbicular, smooth, with irregular longitudinal 
costae ; ears as wide as the shell, nearly equal. — Sower. Min. Conch, t. clviii. 
--..Chalk Marl. 
8. P. orbicularis. — Orbicular, 'much depressed, concentrically striated ; striae 
elevated, sharp ; one valve smooth ; ears nearly equal, broadest at the base. 
Sower. Min. Conch, t. clxxxvi. — In Green Sand. 
7. P. corrwtus Orbicular, much depressed, smooth ; ears small, nearly 
equal ; two obtuse teeth near the ear within each valve. — Sower. Min. 
Conch, t. cciv. — London Clay. 
8. P. obscurus. — Suborbicular, depressed, with obscure arched longitudinal 
rugae upon the surface ; ears large. — Soiver. Min. Conch, t. ccv. f. 1 Under 
Oolite. 
9. P. lens. — Orbicular, convex ; surface marked with diverging arched 
striae ; striae deeply punctured — Sower. Min. Conch, t. ccv. f. 2, 3 — Under 
Oolite. 
10. P. laminatus. — Suborbicular, depressed, striated ; striae arched, diver- 
ging; ears triangular, unequal; the largest plaited. — Sower. Min. Conch, 
t. ccv. f. 4. — Under Oolite. 
11. P. arcuatus. — Orbicular, depressed, with arched, punctured, and diver- 
o'ino- striae upon the surface ; ears large ; the side beneath the largest is 
arched.— .S'ozyer. Min. Conch, t. ccv. f. 5-7 — Middle Oolite. 
12. P. Suborbicular, depressed, striated; striae arched, diverging; 
eai*s unequal ; sides straight. — Sower. Min. Conch, t. ccv. f. 6. — Under Oolite. 
13. V.rigidus. — Orbicular, depressed; strongly striated ; striae arched, di- 
verging ; ears large, unequal, decussated.— Min. Conch, t. ccv. f. 8 — 
Under Oolite. 
14. V.barbatus Orbicular, depressed, transversely striated; rays four- 
teen, those upon one valve spinose; spines long, acute, depressed; ears 
nearly ec^oX.— Sower. Min. Conch, t. ccxxxi. — Urider Oolite. 
15. P. lamellosus. — Orbicular, convex, with concentric erect lamellae upon 
the surface, and diverging striae near the beaks ; ears large, distinct — Sower. 
Min. Conch, t. ccxxxix.— Oolite. 
16. P. 'papyraceus Depressed, obliquely oval, with large unequal rectangu- 
lar ears ; numerous elevated striae, decussated by the lines of growth ; shell 
thm.-— Sower. Min. Conch, t. cccliv. — In shale of the Coal fwmation. 
17. P. asper. — Nearly orbicular, convex on both sides, bearing about seven- 
teen sets of rays (from five to seven in each, according to the age of the 
shell), roughened by subtubular imbricated scales ; margin internally fim- 
briato-crenated ; ears distinct, nearly equal — List. Conch, t. cccclxx.— AS'own 
Min. Conch, t. ccclxx. f. 1. — In Green Sand. 
