COMPLETE GRAU : PECTINIDAE OF THE EASTERN PACIFIC 121 



Iredale, 1939, p. 367, pi. 5, figs. 20, 20a [== Pecten vexillum Reeve, 



1853, sp. 114, pi. 27, figs. 114a, b] ; type locality: Queensland. 



Geographical range: Indian Ocean, from Mauritius eastward; 



East Indies; Queensland, Australia; Philippine Islands; south 



Pacific. 

 Original diagnosis: Le Dr. Jousseaume range ce P. tigris dans un 

 genre Semipalliurn caracterise par des coquilles aplaties, allongees oblique- 

 ment, inequilaterales, a oreillettes tres inegales. 



Additional diagnosis: Shell higher than long and moderately to 

 rather strongly oblique ; right valve moderately convex, left valve flatter ; 

 margins occasionally compressed; hinge line more than y'2 but less than 

 % length of disk; ribs result of corrugations of disk; low radial ridges 

 on ribs and in interspaces, with fine and very profuse concentric lamellae ; 

 anterior auricles longer than posterior and with shallow to moderately 

 deep byssal notch ; ctenolium usually present. 



Remarks: The original diagnosis — shells flattish, obliquely elongate, 

 inequilateral, with very unequal auricles — is brief, but the designation 

 of Pecten tigris Lamarck as type species indicates the author's intention 

 in proposing this genus. 



CoTuptopallium and Bractechlamys were based on species here re- 

 garded as congeneric with Semipallimn tigris. Both are also further 

 examples of Iredale genera in which the diagnoses apply only to the type 

 species. Geographic separation was the basis for his contention that the 

 Australian representatives of such well-known species as Ostrea radula 

 and Pecten vexillum were distinct and must be given new names. Actual- 

 ly, although both species are widely distributed, Australian specimens 

 are inseparable from those found elsewhere. In concluding that the rib- 

 count of Ostrea radula had geographic significance he was mistaken ; the 

 author has long series of that species from many localities throughout its 

 range, the rib-count being not only inconstant, but 9- to 13-ribbed forms 

 often occurring within a single population. In that respect Pecten vexil- 

 lum is identical. 



Several authors have referred both Ostrea radula and Pecten vexil- 

 lum to Decadopecten Sowerby (1839, p. 37); however, the strong 

 plicoid hinge which is the diagnostic feature of that genus is not found in 

 Semipallium. Incidentally, according to Sherborn (1923, p. 1796) a 

 typographical error explains Sowerby 's proposal of the genus as Decato- 

 pecten] the error was corrected by Sowerby (1842b, p. 136). Denti- 

 pecten Gray (1847, p. 200) is a typonym of Decadopecten. 



Complicachlamys is clearly a synonym of Semipallium. The type, 

 Complicachlamys wardiana, is actually the Queensland subspecies of the 



