COMPLETE GRAU : PECTINIDAE OF THE EASTERN PACIFIC 63 



names have been rejected, based his Pseudamusium on their descriptions 

 and figures and was obviously referring to their wtst African shell, 

 despite his errors in giving a description and figures of his own which 

 actually represented the European Pecten septernradiatus. Gmelin cited 

 the descriptions and figures of Lister and Klein and accepted those of 

 Chemnitz, which were erroneous; the actual shell was still the west 

 African one, however, therefore Ostrea hybrida Gmelin is its first bi- 

 nomial and first valid name. The following are synonyms: Pecten exoti- 

 cus Chemnitz, P. dispar Lamarck, P. pseudamusium Sowerby, P. orbi- 

 cularis Sowerby, P. loveni Dunker. 



C. The type species is Ostrea hybrida Gmelin, first validly desig- 

 nated by Dall in 1898. Designations of other species were invalid, and 

 resulted from the errors of Chemnitz, Lamarck and Morch. 



Subgenus PEPLUM Bucquoy, Dautzenberg & Dollfus 1889 



Peplum Bucquoy, Dautzenberg & Dollfus, 1889, pp. 62, 67, pi. 16, figs. 

 10, 11. [Proposed as a subgenus of Pecten.^ Type species: Ostrea 

 inflexa Poli, 1795, p. 160, pi. 28, figs. 4, 5 [= Ostrea clavata Poli, 

 1795, p. 160, pi. 28, fig. 17, designated type by B., D. & D.] ; type 

 locality: Sicily. 



Original diagnosis'. Nous etablissons cette section pour le P. clava- 

 tus qui, par sa forme generale, se rapproche de certains Chlamys ; par la 

 disposition de ses cotes rayonnantes, ressemble a certains Aequipecten 

 (fiexuosus) , tandis que par la conformation de ses valves (valve droit 

 bombee, valve gauche plane) il appartient plutot au groupe des Pecten 

 typiques. La tres petite dimension des oreillettes est bien particuliere. 



Additional diagnosis: Shell of moderate size and either orbicular, 

 obliquely orbicular or slightly higher than long; right valve more convex 

 than left ; ventral margins often flexed in type species and fasciculatum 

 (Hinds), only rarely in septemradiatum (Miiller) ; hinge line short 

 iYztoy^ length of disk). Ribs result of corrugations of disk and strength 

 variable, ranging from shallow and gently sloping to deep and rounded ; 

 central ribs larger and becoming much wider toward ventral margin. 

 Sculpture of disk in inflexum and septemradiatum consisting of very fine 

 to fairly prominent radial ridges and/or very fine radial striae, stronger 

 on left valve than on right ; in fasciculatum of fine radial ridges and pro- 

 fuse concentric lamellae on both valves. Auricles quite small and anterior 

 longer than posterior; riblets fine and sometimes imbricated. Byssal 

 notch shallow; ctenolium absent in type species and adult specimens of 



