PTEPTNOPTCCTEN PAPYRACEUS. 51 



valve. Several specimens of the lefl valve arc crushed and have lost their original 

 shape, and are therefore misleading as to their condition when living. 



8. ornata is easily distinguished from 8. hemisphaerica by the presence of 

 flexuous radiating striae in front, and from 8. laevigata by its more rounded shape 

 and the concentric linear ornament. 



Genus Ptertnopecten, Hall, 1884. 

 Pterinopecten, Hall, 1884. Pal. N. York, vol. v, pt. i, Lamell., p. xii. 



Generic Characters. — Shell Pectiniform, hinge-line long. Posterior ears not well 

 defined, being simple expansions or extensions of the upper lateral margins to the 

 hinge-line. Test ornamented with rays, ears having the same ornament as the rest 

 of the valve, and both valves having an almost identical adornment. 



Observations. — -There can be no doubt of the propriety of separating shells with 

 a prolonged hinge-line and indefinite posterior ears from Aviculopecten, M'Coy ; for 

 the type species of this genus is A. planoradiatus, which was described with 

 A. Ruthveni when the genus Aviculopecten was originally diagnosed in the 'Annals 

 and Magazine of Natural History,' 2nd series, vol. vii. Hall recognises Pterino- 

 pecten in beds of Devonian age in North America, and it seems to have persisted 

 until Middle Coal Measure times in England ; but the genus is not rich in species, 

 one single species only being found, above the Carboniferous Limestone massif and 

 its equivalent, the Yoredale Rocks of Wensleydale and. the North. 



Zittel has evidently mistaken the type of Aviculopecten, for he figures and 

 describes /'. papyraceus as the type, instead of A. planoradiatus, which proves to be 

 the left valve of a shell previously described by M'Coy as /'. tabulatus. 



Pterinopecten paptracetjs, Sowerby, sp., 1823. Plate VII, figs. 7 — 13. 



Pecten papyraceus, Sowerby, 1823. Min. Conch., vol. iv, p. 75, t. 354. 

 Avicula papyracea, Goldfuss, 1834-40. Petref. Deutschl., vol. ii, p. 126, t. 116, 



fig. 5. 

 Pecten papyraceus, Phillips, 1836. Geol. Yorks., pt. ii, p. 213. 

 Avicula papyracea, dc Koninclc, 1842-4. Anini. Foss. Terr. Carb. Belg., p. 136, 



pi. v, fig. 6. 

 Pecten subpapyracea, de Verneuil, 1845. Geol. Russie d'Europe, p. 325, pi. xxi. 



fig. 3. 

 Avicula papyracea, Brown, 1849. Illust. Foss. Conch., p. 159, pi. 61**, fig. 11. 



8 



