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of its surface is covered with fine radiating ribs, alternately more or less 
distinct, nearly imperceptible on the posterior fourth ; these ribs are all crossed 
by more distinct concentric wrinkles. The anterior ear is rather large, rounded 
at the extremity, and separated from the rest of the shell by the byssal notch ; 
its surface is furnished with radiating striae. The posterior ear is unknown 
to me. 
Dimensions . — The length and breadth are about nine millimetres. 
Relations and Differences. — I have dedicated tliis species to Mr. Hardy, 
who has greatly helped Mr. Clarke in his work. It bears some resemblance 
to A. Jonesii, McCoy, from which it differs by the greater number of its 
ribs and concentric folds. 
Horizon and Localities. — A single specimen of this species was found 
at Burragood. 
Aviculopecten cingendus, F. McCoy. 
Fl. XXII, Fig. 8. 
Recten cingendlis, F. McCoj, ISli, Sjnop. Garb. Foss. Ireland, p. 90, pi. 17, fig. 11. 
This shell is small, orbicular and slightly convex. The ears are 
unequal, the posterior ear being very large and rectangular, while the anterior 
ear is rather small, narrow, and rounded at its extremity. The most striking 
^characteristic is the twelve to fifteen concentric folds which ornament the 
surface, the thickness of which increases gradually with their distance from 
the beaks ; these folds are perfectly smooth and disappear imperceptibly 
under the posterior ear. 
Dimensions . — The length is twelve, and the breadth eleven, milli- 
metres. 
Relations and Differences . — This species is rather like A. Sedgwicldi, 
McCoy, the surface of which has concentric folds, but less numerous and 
unlike in profile ; the shell is also more convex and the ears of a different 
shape. 
Horizon and Localities. — A single specimen of this species was found 
by Mr. Clarke in an argillaceous reddish limestone between the Karua River 
and Hungog. In Ireland it has been found at Abbey Bay. 
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