PTEPINOPECTEN GRANOSUS. 57 



Pterinopecten gkanostjs, Sowerby, sp., 1827. Plate X, figs. ] — 3, <>. 



Pecten granosus, Sowerby, 1827. Min. Conch., p. 114, pi. dlxxiv, fig. 2. 



? Portloclc, 1843. Eep. Geol. Londonderry, pp. 436, 437. 



_ _ M'Goy, 1844. Synops. Carb. Foss. Ireland, p. 93. 



— Brown, 1849. Must. Foss. Conch., p. 154, pi. lxv, fig. 10. 

 Aviculopecten granosus, Morris, 1854. Cat. Brit. Foss., 2nd edit., p. 164. 

 M' Coy, 1855. Brit. Pal. Foss., p. 486. 

 — Baity, 1875. Figs. Char. Brit. Foss., p. 113, pi. xxxix, 

 fig. 2. 

 Non — de KonincJc, 1885. Ann. Mus. Eoy. d'Hist. Nat. Belg., 



torn, xi, p. 213, pi. xxxvi, figs. 11, 12. 

 nodtxlosus, de KonincJc, 1885. Ibid., p. 211, pi. xxxvii, figs. 6, 



12—15. 

 blandus, de KonincJc, 1885. Ibid., p. 216, pi. xxxiii, figs. 25, 26; 

 pi. xxxvi, fig. 29. 



Specific Characters. — Shell attaining a fair size, obliquely suborbicular. 

 Antero-posterior and dorso-ventral diameters almost equal. Inequivalve, almost 

 equilateral. The left valve moderately convex, the right nearly flat. The 

 anterior and inferior borders convex, the posterior convex below, sinuous above. 

 The hinge-line straight, equal in length to the greatest transverse diameter of the 

 valve. The umbones placed in front of the centre of the hinge-line, that of the 

 left valve tumid and slightly raised, that of the right valve small and inconspicuous. 

 The anterior cars well marked, triangular, pointed, separated from the valve by a 

 well-defined groove, and projecting beyond the anterior border. The posterior 

 ears not marked off from the valve. The upper border of the posterior ear 

 produced backwards and pointed, its margin falcate. 



Interior. — The hinge-plate is elongate, narrow, and transversely striate. 



Exterior. — The surface is ornamented with numerous radiating ribs, distinctly 

 tuberculated or moniliform, separated by folds, the surface of which is transversely 

 striate. Secondary ribs arise in the grooves between the main ribs, and in large 

 full-grown examples as many as three fine moniliform ribs are seen between the 

 larger ones. In small shells the ribs are more numerous, finer, and closer together. 

 Concentric lines of growth cross tin 1 ribs, some being strongly marked, and always 

 well developed in the position of the posterior ear. 



Dimensions. — PI. X, fig. 2, from the Carboniferous Limestone of Clitheroe, 

 measures — 



Antero- posteriorly .... 65 mm. 



Dorso-ventrally . . . .GO mm. 



Elevation of left valve . . . .10 mm. 



