CARBONIFEROUS FOSSILS OF IRELAND. 89 



PeCTEN iEQUALIS. M'Coy. (PI. XV. fl(T. 13). 



Sj>. C/i.— Orbicular, subtriangular, wider than long ; gibbous ; ears unequal, anterior rounded, posterior 

 pointed, marked with about eight strong ridges, parallel with the outer margin; body of the shell radiated 

 with about seventeen strong, rough, distant ribs, equal in thickness but alternately longer and shorter, rouo-h- 

 cncd by numerous strong, irregular, concentric wrinkles. 



This little species is not remarkable for any -very striking character, excepting, perhaps, the equality of 

 thickness in the radiating ridges, although of unequal length ; the only species it approaches is the P. cancella- 

 tulus, M'Coy, (PL XIV. fig, 9.), from which it differs in the radiating ridges being alternately longer and 

 shorter, and in the Irregularity of the concentric wrinkles. Length two lines, width two and a half lines. 



Pecten asperulus. M'Coy. (PL XVI. fig. 5). 



Sp. Ch. — Orbicular, slightly convex; ears moderate, unequal, anterior rounded, marked with numerous, 

 radiating ridges, crossed by strim parallel with the margin ; posterior pointed and similarly marked ; surface of 

 the shell regularly radiated with numerous sharp, tuberculated stria?, alternating with which are an equal num- 

 ber of much finer spinose strise, the spaces between them strongly plicated transversely. 



This species approaches the P. rugulosus, M'Coy, in general appearance, but is distinguished by the trans- 

 verse striation of the ears, the distinctly tuberculated, radiating ridges, and the intervening spaces, which are 

 smooth in P. rugidosus, having a distinct concentric plication in the present shell. Length about seven lines, 

 mdth seven lines. 



Pecten ARAcmsroroEus. Phil. 



Pecten arachnoideus. Phil. PaL Fos. 



Sp. Ch. — Obliquely ovate, slightly convex ; ears small, nearly equal, acute, smooth, or marked with a few 

 lines of growth ; surface with few distant, sharp, radiating sulci, forming between them broad, flat, unequal ribs, 

 crossed by close, fine, concentric strije. 



This species occurs of considerable size, but I have not been able to satisfy, myself as to whether the obH- 

 quity be real or accidental. Length one inch nine lines, width one inch ten lines. 



Pecten arenosus. Phil. 



Pecten arenosus. Phil. Geol. York. 



Sp. Ch. — Shell subtriangular, convex; ears large, square, distinct; surface with very numerous, sharp, ra- 

 diating ridges, alternately larger and smaller, decussated by very fine, concentric striae. 



This species has the radiating ribs very numerous and close together, alternately longer and shorter ; un- 

 der the lens they appear regularly reticulated by sharp, transverse lines ; the eai's are large, rectangular, unequal, 

 radiatingly striated. Length one inch, width one inch two lines. 



Pecten bellis. M' Coy. ( PL XV. fig. 15). 



Sp. Ch. — Ovate, convex ; ears moderate, nearly equal, radiated with few, distant, rounded ridges, the in- 

 tervening spaces being sharply striated parallel to the external margin; body of the shell marked with about 

 thirty-two sharp, radiating ridges, alternately larger and smaller ; interspaces nearly smooth, or faintly marked 

 by irregular lines of growth. 



This little shell approaches the P. gentilis, Sow., very much in general appearance, but has more than 

 twice the number of radiating ridges, and is shorter in proportion to the width. Length three lines, width 

 three lines. 



Pecten cancellatulus. M'Coy. (PL XIV. fig. 9)- 



Sp. Ch. — Orbicular, convex; ears large, square; surface with about fifteen thick, radiating ribs, which are 

 cancellated and tuberculated by thinner, transverse ones. 



Z 



