PECTEN. 145 
Family—PECTINIDA,! Lamarck. 
Genus—Prcrren, Miller, 1776. 
(‘ Prodr. Zool. Dan.,’ p. 248.) 
Sub-genus—Syneyctonema, I’. B, Meek, 1864. 
(‘Check List of Invert. Foss. N. America, Cret. and Jur.,’ Smithson, Misc. Coll. 177, pp. 7, 31.) 
Syncyclonema should probably be united with Entolium, as has been suggested 
by Philippi, since in the former the concentric ornamentation of the right valve is 
sometimes incompletely developed, and the ears have, in some cases, a more or less 
well-marked dorsal prolongation ; on the other hand, in some forms of Hitolium the 
dorsal prolongation of the ears is insignificant. Syneyclonema is the earlier of the 
two names. The type of Mntolium’ is Pecten demissus, Phillips ; this has also been 
taken by Verrill? as the type of Protamusium. 
PEcTEN (SyNCYCLONEMA) orBICULARIS, Sowerby, 1817. Plate XXVII; and Text- 
fig, LE: 
1817. Prcren orpicunaris, J. Sowerby. Min. Conch., vol. ii, p. 193, pl. elxxxvi. 
1819. = sa Lamarck. Anim. sans Vert., vol. vi, pt. 1, p. 182. 
1822. — LAMINOSUS, G. Mantell. Foss. 8S. Downs, p. 128, pl. xxvi, figs, 8, 22. 
1825. — ORBICULARIS, Defrance. Dict. Sci. nat., vol. xxxviii, p. 252. 
1 Recent accounts of the classification of the Pectinida have been given by—aA. E. Verrill, “ A 
Study of the Pectinid, with a Revision of the Genera and Sub-genera,” ‘Trans. Connecticut Acad.,’ 
vol. x (1897), p. 41. F. Sacco, “ Molluschi dei Terreni Terziarii del Piemonte e della Liguria ;”’ pt. 
24, “ Pectinide,’ 1897. W. H. Dall, ‘Tertiary Fauna of Florida,” ‘Trans. Wagner Free Inst. of 
Philadelphia,’ vol. iii, pt. 4 (1898), pp. 689—758. E. Philippi, “ Beitriige zur Morphologie und 
Phylogenie der Lamellibranchier:” (1) “ Hinnites und Velopecten,” ‘ Zeitschr. der deutsch. geol. 
Gesellsch.,’ vol. 1 (1898), p. 597; (2) “ Zur Stammesgeschichte der Pectiniden,” ibid., vol. lii (1900), 
p. 64, A. Loeard, ‘ Faune Malacologique Francaise,” xi, ‘‘ Monographie des Esptces appartenant au 
Genre Pecten,” ‘Ann. Soc. Linn. de Lyon,’ vol. xxxiv (1888), p. 133. C. Depéret and F. Roman, 
“Monographie des Pectinides néogtnes de l'Europe et des régions voisines,” ‘Mem. Soe. géol. de 
France (Paléont.),’ vol. x, pt. 1 (1902). 
* Meek, “Geol. Survey of California,” ‘ Geology,’ vol. 1, Appendix B (1865), pp. 478, 479. 
8 «Trans. Connect. Acad.,’ vol. x (1897), p. 71. 
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