64 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 23 



septemradiatum, present in fasciculatum and juvenile specimens of 

 septemradiatum. 



Remarks: Although Bucquoy, Dautzenberg & Dollfus designated 

 Ostrca clavata as the type species and regarded O. inftexa as a synonym 

 "or perhaps a variety," the latter has priority because its description 

 precedes that of O. clavata on page 160 of Poli's work. 



This subgenus is quite similar to Flexopecten in some respects, but 

 can be easily distinguished by the shorter hinge line and correspondingly 

 shorter auricles. 



The presence or absence of flexed ventral margins in P. inilexum. 

 and P, fasciculatum is the result of individual variation, as can be seen 

 by a long series of specimens from any one locality. In such genera as 

 Decadopecten, Flexopecten, Mesopeplurn and Seinipallium the same kind 

 of variation within species is common. 



Pecten septemradiatus Miiller, here referred to Peplurn, has been 

 regarded as the type species of Pseuda?nussiujn by some authors; the 

 matter has been discussed in this paper under that genus. Synonyms for 

 P. septemradiatus are: Ostrea pes-lutrae Linne, 1771, p. 547 (comments 

 on apparent priority below) ; Pecten triradiatus Miiller, 1776, p. 248; 

 Pecten Pseud-a?nusiufn Chemnitz, 1784, p. 298, tab. 63, figs. 601, 602; 

 Pecten Danicus Chemnitz, 1795, p. 265, tab. 207, fig. 2043; Pecten 

 aspersus Lamarck, 1819, p. 167; Pecten Dumasii Payraudeau, 1826, p. 

 75, pi. 2, figs. 6, 7; Pecten nebulosus Brown, 1835, p. 9, fig. 1 ; Pecten 

 Jamesoni Forbes in Smith, 1839, p. 106, pi. 2, fig. 1. The apparent 

 priority of Ostrea pes-lutrae Linne is not accepted here; it is quite 

 certainly identical with P. septetnradiatus, but the holotype (if any 

 specimen was designated) is not known, the original description is as 

 misleading as many others of Linne, and the figures of Gualtieri, Argen- 

 ville and Lister that Linne cited are of little value. Dodge (1952, p. 

 196) has given an interesting and thorough discussion of the status of 

 pes-lutrae, although the present author does not agree with his conclu- 

 sion. 



The most distinctive features of this subgenus are the plicate ribs 

 which increase greatly in width toward the ventral margin and the very 

 small auricles. 



Peplum is represented by three living species: inflexum (Poli) in the 

 Mediterranean, septemradiatum (Midler) in the eastern Atlantic, and 

 fasciculatum (Hinds) in the eastern Pacific. 



