COMPLETE GRAU : PECTINIDAE OF THE EASTERN PACIFIC 67 



Forme en general ovale-oblongue ; valves convexes, subegales; cotes 

 radiales plus ou moins nombreuses, souvent squameuses; oreillettes ine- 

 gales, surtout sur la valve droite dont I'oreillette anterfeure, allongee, 

 presente a sa base un sinus plus ou moins profond qui porte sur son bord 

 inferieur une rangee de petites denticulations (filiere, ctenolium, pectinid- 

 ium, dents pectinidiales). Surface interne costulee, commissure des valves 

 laciniee par les cotes. 



Additional diagnosis: Shell moderately convex, left valve usually 

 more so than right; a little higher than long and often oblique; ribs 

 rather strong in most species, frequently increasing by bifurcation and 

 occasionally fasciculated ; riblets present in most species ; ribs and riblets 

 usually having spines or scales; anterior auricles larger than posterior; 

 byssal notch moderate to large and ctenolium present. 



Remarks: In a paper on the status of the Bolten catalogue, Dr. 

 Harald A. Rehder (1945, p. 52) said, "It may be emphasized here again 

 that the names proposed in this work should, according to the Inter- 

 national Rules, be credited to Roeding, as Bolton [sic] furnished the 

 names only, and not the 'name and (italics mine) its indication, defini- 

 tion or description' (last part of Article 21, International Rules of 

 Zoological Nomenclature)." 



Zygochlamys was based on a single feature: the fact that the ribs of 

 the right and left valves differ in structure. That feature is possessed by 

 so many species of Pectinidae that it cannot be regarded as a distinction 

 of supraspecific value. 



In Mimachlamys, as in so many other genera and subgenera proposed 

 by Iredale, the diagnosis applies only to the type species. Despite that 

 fact, he referred to the unit a number of species which do not agree with 

 the diagnosis. 



Scaeochla?nys and Belchlamys of Iredale were also based on features 

 of only specific value. 



Coralichlamys was proposed by Iredale with distortion as the only 

 really distinctive diagnostic feature. Distortion is found in a number of 

 completely unrelated species; furthermore the type species itself, C. 

 acroporicola Iredale (actually Pecten madreporarum Petit in Sowerby), 

 is quite inconstant in that respect. 



Key to the eastern Pacific Species of Chlatnys 



1. Shell rather thin and with spinose sculpture 



2. Ribs wide, angular plications of disks and consisting of three 

 spinose riblets 



