CARBONIFEROUS FOSSILS OF IRELAND. 97 



Pecten mundus. M'Coy. (PI. XYII. fig. 5). 



S]>. Ch. — Ovate, convex; ears large, sliglitly pointed, equal, without radiating ridges, closely striated, 

 parallel to the margin ; surface with distant, very fine, radiating ridges, alternately larger and smaller, decus- 

 sated by numerous, fine, concentric wrinkles. 



In this species the radiating striaj are remarkably slender, and three or four times their diameter apart; 

 the ears are perfectly equal in size and shape, transversely striated ; the concentric strias of the body of 

 the shell are fine, sharp, and about the same distance apart as the longitudinal ones, but rather irregular. 

 Length four and a half lines, width four lines. 



Pecten Murchisoni. M'Coij. (PI. XVIII. fig. 3). 



Sp. Ch. — Shell longitudinally ovate; surface radiated with about twenty thick, nodular, ribs, alternating 

 with an equal number of smaller ones, the intervening spaces flat, smooth; ears large, equal, square, with three 

 or four ribs. 



This elegant species is marked by aliout eighteen or twenty large, distant, radiating ridges, which, in 

 some lights, appear slightly tubercular ; between these are an equal number of small ribs, the spaces between 

 which are perfectly even and smooth ; the ears large and square, equal, smooth, with a few radiating, round 

 ribs, four on one side, and two on the other ; crossed on one ear by two ridges equalling the others in thickness, but 

 running parallel with the lateral margin ; at each intersection of the ribs a large tubercle is formed. Length 

 one inch and a half, breadth one inch and a quarter. 



Pecten orbiculatus. M'Coy. (PI. XIV. fig. 8). 



Sp. Ch. — Orbicular, very convex, smooth; ears acute, nearly equal, marked with radiating ribs. 

 This curious species is closely allied to the P. gibhosus, M'Coy, but is at once distinguished by the form 

 of the ears, and their being marked with radiating striae. Length five lines, width six lines. 



Pecten ovatus. M'Coy. (PL XIV. fig. 11). 



Sp. Ch. — Ovate, flat, ears large, square; surface with about seventeen equal, distant, tuberculated ribs, the 

 spaces between which are sharply striated transversely. 



This species has a more regular ovate form than any other with which I am acquainted ; the ears extend 

 very nearly the width of the shell, and are radiatingly ribbed ; the radiating ribs on the surface are regularly 

 tuberculated, and of equal size, although I have occasionally seen, as in the magnified figure, a very slender, 

 irregular rib, tuberculated like the rest, extending up a short way from the margin ; the intervening spaces are 

 delicately, but sharply striated across. Length eight lines, width seven lines. 



Pecten pera. M'Coy. (PI. XV. fig. 19). 



Sp. Ch. — Ovate, slightly convex, front broad ; ears large, unequal, anterior one rectangular, posterior larger, 

 pointed ; surface radiated with very numerous, close, fine striae, alternately larger and smaller, crossed near the 

 margin by sharp, concentric lines ; ears with about ten or twelve sharp, radiating strife, similar to those of the 

 body, and crossed by very delicate striffi. 



From the vridth, and slight convexity of the front, the outline resembles a bag or satchel. I am not sure 

 whether the radiating strice are spinose ; in some lights they seem to be so, but the character is doubtful. 

 Length ten lines, width one inch. 



2B 



