62 CARBONIFEROUS LAMELLIBRANCHIATA. 



in PL VIII, fig. 3, it will be seen that the wing is comparatively smaller in young 

 examples, though not so small as in the specimen under discussion. The general 

 sculpture of the shell has induced me to place it with M'Coy's species for the 

 present. 



Pterinopecten meleagrinoides, M'Coy, sp., 1844. Plate XVII, figs. 20 — 23. 



Pecten meleagkinoides, M'Coy, 1844. Synops. Carb. Foss. Ireland, p. 96, pi. xvi, 



fig. 3. 



Specific Characters. — Shell of medium size, truncato-orbicular, convexity of the 

 left valve more than that of the right valve. The anterior and lower borders 

 rounded, the posterior truncate, nearly straight, slightly falcate above. The hinge- 

 line straight, of moderate length. The umbones broadly tumid and pointed, placed 

 in front of the centre of the hinge-line. The anterior ear of the left valve depressed 

 and well defined from the valve, comparatively small and triangular. The anterior 

 ear of the right valve separated from the valve by a deep and long byssal slit, the 

 ear comparatively narrow and of moderate length. No posterior ear, but each 

 valve compressed and flattened into the postero-superior angle, which is not pro- 

 duced, the hinge-line being only slightly pointed. 



Interior. — Unknown. 



Exterior. — The surface of both valves is ornamented with alternately large and 

 small, round, radiating ridges, the larger ribs only rising at the umbo. The spaces 

 between the ribs are crossed by concentric ridges, much less strong than the 

 radiating ribs. Towards the posterior superior angle the ribs are wider apart and 

 the intervening surface smoother. The anterior ears are almost smooth in the left 

 valve, but concentrically imbricate in the right. 



Dimensions. — PI. XVII, fig. 22, from Thorpe Cloud, measures — 



Antero-posteriorly . . . .28 mm. 



Dorso-ventrally . . . .22 mm. 



Localities. — England: the Carboniferous Limestone of Thorpe Cloud and 

 Castleton, Derbyshire. Ireland : no locality is given in Griffith's list for this shell 

 ('Journ. Geol. Soc. Dub.,' vol. ix, p. 100). 



Observations. — Unfortunately the type of P. meleagrinoides, M'Coy, has dis- 

 appeared, but, judging from the figure and description, I think there need be no 

 doubt of the propriety of referring my specimens to this species. P. meleagrinoides 

 is distinguished by its short hinge-line posteriorly, in this point differing from 

 other species of the genus, to which, however, it must be referred, because it has 

 no defined posterior car. 



I have; been fortunate enough to find both valves, and, as in other species of the 



