Pecten. 
MOLLUSCA* BIVALVIA. 
387 
18. P. obliqum. — Obliquely oval, conveftc on both sides ; radii very nume- 
rous, roughened by semicircular imbricated scales ; ears large, distinct.— 
Sower. Mm. Conch, t. ccclxx. f. 2.— In Green Sand. 
19. P. cinctus — ^Orbicular, gibbose, longitudinally striated, imbricated | 
edges of the laminae thin, erect ; ears small ; edge entire — Sower. Min. 
Conch, t. ccc\sx.i.-~-Under Oolite ? 
20. P. sulcafus. — Obliquely orbicular, with twenty obscurely tripartite 
rays, the intermediate spaces longitudinally striated, the whole rough with 
minute scales ; internally sulcated ; ears nearly equal. — Sower. Min. Conch, 
t. cccxciii. f. 1. — Suffolk Crag. 
21. P. gracilis — ‘Orbicular, thin, convex, with many small longitudinal 
ridges, concentrically striated ; striae close, elevated, sharp ; ears unequal ; 
margin entire. — Soicer. Min. Conch, t. cccxciii. f. 2. — In Crag, 
22. P. striatus. — Oval, convex ; valves nearly equal, with numerous smooth 
or scaly ridges ; within plain, margin entire ; ears equal, rather large- — Sower. 
Min. Conch, t. cccxciv. f. 2, 3, 4.— In Crag. 
23. P. nitidus — Obovate, one valve nearly fiat, with numerous, nearly 
smooth ridges, the interstices minutely striated transversely, the other valve 
convex, with as many crenulated ridges ; margin entire ; ears nearly equal 
..—Mant. Suss. 202. t. xxvi. f. 4-9. — Sower. Min. Conch, t. cccxciv. f. 1. — In 
Chalk. 
24. P. ohsoletus ? — Equivalved ; ears very unequal ; surface finely striated ; 
striae obliquely diverging. — Sower. Min. Conch, t. nxli — In Crag. 
25. P. princeps Orbicular, compressed ; decorated with ninety rounded 
nearly equal radii, surmounted with erect concave scales ; ears large, un- 
equal, squamose ; valves equal. — Sower. Min. Conch, t. Dxlii. f. 2.— In Crag. 
26. P. annulatus — -Orbicular, convex ; numerous thin, erect, concentric 
laminae, and fine longitudinal striae ornament the surface, passing over the 
large eox^.-^Sower. Min. Conch, t* nxlii. f 1 — Loiver Oolite. 
27 . P. Convex, rather longer than wide, concentrically striated 1 
ribs about twenty, prominent, close beset with thick elevated scales, which 
are less numerous upon the left valve ; ears nearly equal. (P. varius^ Geol. 
Surv. Yorksh. 223. t. ix. f. 9.) — Sower. Min. Conch, t. Dxliii. f. 1, 2. — Lower 
Oolite. 
28. P. vagans — Hather convex, a little longer than wide ; ribs eleven, 
large, convex, decorated with large erect concave scales, that are very close 
upon the right, but distant upon the left, valve ; ears nearly equal, crossed 
by larger scales.— (P. sulcatus,, Geol. Surv. York. 233. t. ix. f. 3.) — Sower. 
Min. Conch, t. nxliii. f. 3, 4, 5 — Lower Oolite. ^ 
29. P. triplicatus. — Subtriangular, longitudinally striated, with three deep, 
longitudinal furrows, which form angular plicje on the front ; margin crenu- 
lated.— Geol. Suss. 128. t. xxv. f. 9. — In Grey Chalk Marl. 
30. P. laminosus — Suborbicular, much depressed, concentrically laminated, 
ears nearly equal. — Mant. Geol. Suss. 128. t. xxvi. f. 8 — In Grey Chalk 
Marl. 
31. P. dissimilis — Suborbicidar, slightly lengthened, the right or lower 
valve with numerous ribs, slightly scaly ; ears nearly equal, ribbed trans- 
versely and longitudinally ; the left or upper valve concave, regularly mark- 
ed concentrically with flat obsolete ribs, which become scaly in crossing the 
longitudinally ribbed ears. In my cabinet, from the shale and limestone of 
the Independent Coal formation In the concavity of the left valve, it agrees 
with the recent P. marinus and P. Jacobceus. 
B b 2 
