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valve by a sharp sinuosity, while the posterior ear is badly defined, and 
terminates in a right angle. The whole surface is pretty smooth and shows 
only very indistinct lines of growth ; the extremity of the anterior ear is 
folded transversely. 
Dimensions. — The length is seven, and the breadth nine millimetres. 
Delations and Differences . — According to McCoy this species dilfers 
from A . variahilis, so common in the Carboniferous shales of Ireland, only by 
the transverse folds on the anterior ear. It cannot be confounded with A. 
consimilis, McCoy, because it is relatively broader, its apical angle is smaller, 
and its anterior ears are not reticulated. 
Horizon and Localities. — According to McCoy it is common in the 
shales of Dunvegan. Mr. W. B. Clarke found it at Burragood and Wollon- 
gong. 
Aviculopecten knockonniexsis, F. McCoy. 
Decten knockonniensis, A McCoy, 1844, Syuop. Carb. Eoss. Ireland, p. 95, pi. 17, fig. 4. 
This is a small, nearly circular, inequivalved shell, as broad as long, 
and slightly ventricose. The surface of the left valve only is ornamented 
with numerous, small, radiating, similar, simple ribs, separated by small 
furrows rather broader than the ribs, and crossed by nearly imperceptible 
lines of growth. The right valve has on its surface from twelve to fourteen 
radiating folds, originating at the beak, and a trifle thicker than those which 
spring up afterwards at some distance from the beaks ; all these folds are 
interrupted at very short distances by concentric rings of growth, giving 
rise to small imbrications, thus making the surface more or less wrinkled. 
The ears are very unequal, the posterior ears are pointed, and the anterior 
ears rounded at their extremities ; both show radiating ribs, crossed by lines 
of growth parallel with the margins. 
Dimensions. — Length and breadth are both about ten millimetres. 
Horizon and Localities. — It is found in the Carboniferous Limestone 
of Ireland, and on tlie banks of the Kama Biver, N.S. Wales. 
Aviculopecten Hardyi, L. G. de Koninck. 
PI. XXII, Pig. 9. 
This is a small, suboval, slightly oblique shell, nearly as long as broad, 
not very convex, and with rather pointed beaks. The anterior three-quarters 
