CARBONIFEROUS FOSSILS OF IRELAND. 99 



tlic cars, however, seem to fix it on the memory; the radiating ridges of the body arc but slightly roughened 

 by an obscure nodulation, the spaces between them are slightly concave and smooth. Length ten lines, width 

 eleven lines. 



Pecten sclerotis. M'Coy. (PL XVL fig. 4). 



Sp. Ch. — Longitudinally ovate, depressed, ears unequal ; surface with numerous longitudinal, rough ribs, 

 alternately larger and smaller ; pointed ear, with obtuse strite parallel to the margin, and irregularly tuber- 

 culated. 



Although the only specimen 1 know of this shell is imperfect, yet it is not likely to be confounded with any 

 other of the genus ; it comes nearer to the P. Murchisoni, INI'Coy, than perhaps any other species, but has nearly 

 three times the number of ribs, and differently formed ears. The radiating ribs are narrow, rounded, and closely set 

 with small, erect scales ; the spaces between them are deep, concave, and smooth : there are about thirty of the 

 principal ribs, and an equal number of intervening shorter and thinner ones ; the pointed ear, which is the only 

 one preserved in the specimen, has, near the base, numerous smooth, obtuse strire, the remaincr of it being co- 

 vered with rough, irregular tubercles. The specimen is too imperfect to give the measurements correctly. 



Pecten Sedgwickh. M'Coy. (PL XIV. fig. 4). 



Sp. Ch — Longitudinally ovate, convex; ears acute, surface smooth, with about ten broad, triangular con- 

 centric ridges; the ears are ridged parallel with the margin. 



This singular species is concentrically marked with broad, triangular ribs, somewhat like those of Posido- 

 nia Becheri; the surface is otherwise perfectly smooth. I have dedicated this species to Professor Sedgwick, 

 to whose zeal we are indebted for the unique specimen figured on the plate. 



Pecten segregatus. i/'Coj/. (PL XVII. fig. 3). 



Sp. Ch. — Longitudinally ovate, slightly convex; ears unequal, one falcate, the other rounded ; surface ra- 

 diated with very distant, narrow ridges, every fifth one twice the size of the others, alternately larger and 

 smaller; ears also radiated with similar, very distant ribs; interstitial spaces broad, flat, smooth. 



This singular species is easily recognized by the great distance which the naiTow, radiating ridges are 

 asrmder, and the flat, smootli spaces between them ; they are about a line apart in full-grown shells, and about 

 the thickness of a fine thread. The specimens are all imperfect ; one of them, however, is one and a half 

 Inches long. 



Pecten semiciecularis. M'Coij. (PL XVII. fig. 10). 



Sp. Ch. — Shell nearly flat, wider than long, front margin semicircular; anterior ear small, square at the 

 extremity, with three close, round, radiating ridges, crossed by sharp stria3, jjarallel to the margin ; surface of 

 the shell closely set with very fine, numerous, equal, radiating ridges, increasing in number towards the margin ; 

 intervening spaces flat, transversely striated. 



This fine species is so much depressed as to appear nearly flat ; the radiating ridges are smooth, very thin, 

 and numerous, new ones being continually added towards the margin ; they are more than their own diameter 

 apart. Length two inches two lines, width three inches. 



Pecten semistriatus. M'Coy. (PL XVII. fig. 9). 



Sp. Ch. — Orbicular, convex, ears unequal ; surface smooth, with the exception of a broad border round 

 the margin, which is marked with radiating strise, forming between them broad, unequal ribs, very sliglnly 

 convex. 



