CARBONIFEROUS FOSSILS OF IRELAND. 91 



Tins large species, like tlie P. Jacobaus, has the left valve concave outwardly, in which it differs from all 

 tlie other Pala;ozoic species. Length three inches three lines, width three inches eight lines. 



PeCTEN CONCENTKICO-STRIATUS. M'Coif. (PI. XIV. fig. 5). 



Sp. Ch. — Transversely obovate, or nearly orbicnlar, convex; ears very large, unequal, radiatingly striated; 

 anterior narrow, subtruncate at the extremity, deeply divided from the body of the shell ; posterior ancnilar, 

 pointed ; surface with delicate, rather distant, concentric strio3. 



This is a wide species; the ears are large, unequal, and marked with radiating ribs, decussated by the lines 

 of growth ; the surface is marked with rather distant, rounded, concentric stri^, the spaces between which are 

 smooth ; the hinge-line in well-preserved specimens is dentated. Length ten lines, width eleven lines. 



Pecten coNoiDEus. M'Coy. (PL XVII. fig. 2). 



Sp. Ch. — Longitudinally ovate, subtriangular, convex valve very gibbous ; ears large, equal, slightly 

 pointed ; radiating strias numerous, smooth, equal, rounded, about their own diameter apart, spaces between 

 them flat, smooth. 



This species is very inequivalve; the convex -»alve is very gibbous; the beak large and inflated; the ears 

 are nearly equal, and without radiating striae. Length one inch, width eleven lines. 



Pecten consimilis. M'Col/. (PI. XV. fig. 16). 



Sp. Ch. — Elongate, oval, convex, smooth; ears very small, unequal; posterior ear largest, rounded at the 

 extremity, deeply divided from the body of the shell, and reticulated with strong, radiating, and concentric 

 ridges, anterior ear very small, rectangular, with transverse stria. 



This species closely resembles the large P. ehngatus, M'Coy, and P. depilis, M'Coy, in form, and in tlie 

 small size of the ears ; it is distinguished from both, however, by the reticulation of the larger ear. In the 

 present instance the character is of much importance, as from its general size and form it might readily be con- 

 founded with the P. depilis. Length three lines, width two lines. 



Pecten deoknatus. Phil. 



Pecten deornatus. Pkil. Geol. York. 



Sp. Ch. — Nearly orbicular, flattened; ears small, acute, equal; surface smooth, with irregular, concentric 

 wrinkles. 



This species has very little to attract the attention of the Palaeontologist, being neither characteristic of any 

 particular stratum, or remarkable for its beauty, scarcely even afibrding a specific character. Length seven 

 lines, width six lines. 



Pecten depilis. 31' Co^. (PI. XVL fig. 11). 



Sp. Ch. — Lengthened, ovate, convex, smooth; ears small, unequal, striated parallel with the outer margin, 

 posterior ear rounded, anterior ear half the length of the posterior, rectangular ; hinge-line less than the width 

 of the shell. 



This is one of the very few smooth species of Pecten found in the mountain limestone. Length three 

 lines, width two and a half lines. 



■ Pecten dissimilis. Flem. 



Pecten dissimilis. Flem. Brit. Anim. (Not of Pkil.) 

 Sp. Ch. — Nearly orbicular ; right valve slightly convex, with obtuse, alternately larger and smaller, radiating 

 ribs ; the other valve flat, or slightly concave, with sharp, imbricating, concentric striae. 



