COMPLETE GRAU : PECTINIDAE OF THE EASTERN PACIFIC 57 



Remarks : This species is here referred to Hyalopecten because of the 

 undulations of the disk (which are functional rather than the result of 

 environment, as in some species of Delectopecten) and the small but 

 well-developed auricles (similar to those of some specimens of the type- 

 species). The reticulate sculpture of the disk distinguishes it from other 

 species of the subgenus. 



Geographical range: Reported only from the type locality and from 

 U.S. Fish Commission station 3407, near the Galapagos Islands, in 885 

 fathoms. 



Genus PSEUDAMUSSIUM H. & A. Adams 1858 



Pseudamussiu?n Herrmannsen, 1847, p. 340. [Invalid; no diagnosis or 

 indication; no type species designated.] 



Pseudatnussiurn Morch, 1853, p. 59. [Invalid publication (sales-cata- 

 logue) ; no type species designated; both species cited incorrectly 

 synonymized. See Re?narks below.] 



Pseudamussium H. and A. Adams, 1858, p. 553. [Proposed as a sub- 

 genus of Pecten.^ Type species: Ostrea hybrida Gmelin, 1791, p. 

 3318. [Gmelin's locality "in mari norwegico" in error; species based 

 on Pseud-amusium of Lister, Klein and Chemnitz; Lister and 

 Klein pre-Linnean and Chemnitz' figures erroneous; Chemnitz' 

 specific names rejected; species living off west Africa. First valid 

 designation of type by Dall, 1898, p. 751. Synonyms: Pecten exoti- 

 cus Chemnitz, 1795, p. 262, tab. 207, figs. 2037, 2038; Ostrea exo- 

 tica Dillwyn, 1817, p. 259; Pecten dispar Lamarck, 1819, p. 173; 

 Pecten Pseudamusium (Klein) Sowerby, 1842, p. 56, pi. 19, figs. 

 211, 212, pi. 20, fig. 243; Pecten orbicularis Sowerby, 1842, p. 57, 

 pi. 20, figs. 231, 232; Pecten Loveni Dunker, 1853, p. 44, pi. 9, 

 fig. 31. For type localities, see Remarks below.] 



Palliolum Monterosato, 1884, p. 5. [Proposed as a section of Pecten.] 

 Type species: Pecten incomparabilis Risso, 1826, p. 302, pi. 11, fig. 

 154 [= p. Testae Bivona in Philippi, 1836, p. 81, pi. 5, fig. 17. 

 Living in western Atlantic, from Norway to west Africa, and in 

 Mediterranean.] 

 Original diagnosis: Shell fan-shaped, thin, sub-equivalve ; valves 



longitudinally plicate, smooth or finely striated. (H. & A. Adams) 



Additional diagnosis: Shell a little higher than long, thin but opaque 



and rather small, only unusually large specimens of Pseudamussium 



hybridum (Gmelin) or P. tigerinum (Miiller) (1776, p. 248) attaining 



height of 25 to 28 mm. Valves moderately and nearly equally convex, 



