212 
DESCRIPTION OF THE FOSSILS. 
Remarkably arched, posterior side steeply ridged ; surface imbricato-striate. It 
grows very much larger. 
G. squamosa. Ph. PI. VI. fig. 9- Holland. 
Arched, posterior side ridged ; surface squamoso-striate. 
G. laminosa. Ph. PI. VI. fig. 10. Bolland ; Colsterdale. 
Less arched than G. lunulata and with a convex rather than ridged posterior side. 
G. inconspicua. Ph. PI. VI. fig. 13 . Castleton. 
The chief difference between this and the preceding form is the want of the strong 
posterior convexity. 
Pecten hemisphericus. Ph. PI. VI. fig. 16. Bolland. 
Lower valve very convex, circular, the sides gradually changing into the ears ; con- 
centrically squamoso-striated. (It may possibly be avicula.) 
P. ellipticus. Ph. PI. VI. fig. 15. Bolland, 
An oval (smooth ?) depressed species, with short ears. 
P. dissimilis. Flem. PI. VI. fig. 17. (19 ?) Bolland ; Linlithgow. 
One valve concentrically and sharply striated ; the other with radiating rough small 
ridges. 
P. arenosus. Ph. PI. VI. fig. 20. Colsterdale; Bolland; Derbyshire ; 
Kildare ; Ivulkeagh, &c. 
The shell a quadrant of a circle, with rather short square ears ; radiating stria; very 
numerous, alternately larger ; minutely crenulated with many sharp circular strim. 
P. anisotus. Ph. PI. VI. fig 22. 
Rather oblong, oblique, with very unequal reticulated ears; surface obscurely 
radiated. 
P. plicatus ? Sow. PI. VI. fig. 21. 
Nearly orbicular, lower valve convex, with numerous nearly smooth radiating ribs ; 
(ears without radiating ribs ?) If the last character be constant, it is not the same as 
Sowerby’s shell. 
P. stellaris. Ph. PI. VI. fig. 18. 
Shell quadrantal, with about fifteen strong smooth rounded ribs. 
P. simplex. Ph. PI. VI. fig. 27. 
Lower valve tumid, with strong radiating furrows over all the surface. Upper 
valve, fig. 27 , much flatter, with corresponding but shallower furrows. 
P. interstitialis. Ph. PI. VI. fig. 24. Hawes ; Bolland. 
With about sixteen narrow, sharp, rough radiating ribs, — the intervening spaces 
with three striae or finer ribs. A specimen in Mr. Gilbertson’s collection has stronger 
ribs. Near the beak the ribs are alternately larger and smaller, ears acute. 
