130 
PECTEN striatus, 
TAB. CCCXC1 N.—figs. 2, 3 and 4. 
Spec. Char. Oval, convex; valves nearly 
equal ; with numerous smooth or scaly 
ridges ; within plain ; margin entire ; ears 
unequal, rather large. 
The width is five sixths of the length; the ridges are 
irregular, but nearly equal. In some specimens they 
have rather distant obtuse crenulations, or scales upon 
them; in others they are wholly smooth, perhaps from 
wear : the shell is rather thick and shews within it but 
slight signs of the ridges. 
Found in the Crag at Holywells, by Mrs. Cobbold, and 
at Woodbridge by the Rev. Mr. Leathes : the speci- 
mens with scales upon the ridges, differ in no other 
respect from the smooth ones, and both are found of 
various sizes ; it is possible the latter may have been 
worn before they were changed into Crag. 
PECTEN~ nitidus, 
TAB. CCCXCIV — fig, 1. 
Spec. Char. Obovate, one valve nearly flat, 
with numerous, nearly smooth ridges, the 
interstices minutely striated transversely, 
the other valve convex with as many crenu- 
lated ridges ; margin entire ; ears nearly 
equal. 
Syn. Pec ten nitida, Mantell Geol. Sussex , p . 
202. tab. 26. f. 4 and 9. 
Pecten cretosus, and P, arachnoides, De 
France , llrogniart and Cuvier Geo . de Paris 
383 and 384 . tab. 3.f. 7 and 8. ed . 1822. 
A rather broader shell than the last, much resembling 
it, but well distinguished by the fineness of its concentric 
striae, the flatness of one valve, and thinness of both 
valves; the ridges upon the convex valve are decidedly 
crenulated or granulated, while those of the other are 
mostly smooth, a circumstance that has apparently led 
Mr. De France to make two species of them. 
By no means a rare Shell in Chalk, but so excessively 
thin that it is seldom found perfect; the dissimilarity 
of the two valves is proved by specimens in which they 
still remain applied together, probably M. de France 
never met with a pair, or he would have observed this ; 
the flatter valve is sometimes nearly as convex as the 
other. 
