COMPLETE GRAU : PECTINIDAE OF THE EASTERN PACIFIC 11 



It much resembles Amussium lucidum Jeffr., from which it is distin- 

 guished by the colored zones and by the diverse sculpture, principally 

 the radiating threads. 



Additional diagnosis: Shell thin, flattish, gaping laterally, and 

 usually higher than long ; right valve flexed near ventral margin ; auricles 

 of equal or near-equal size; no byssal sinus. Sculpture absent on some 

 species ; when present, consisting of fine concentric and/or radial threads. 

 Internal lirae reaching to about center of disk, occasionally farther; 

 lirae always white. 



Remarks: De Gregorio's reference to blood-colored red rays must 

 be disregarded. Gale (Grant & Gale, 1931, p. 232-233) commented, 

 "It seems hardly possible that the red color is the original color of the 

 shell, if the IVIiocene age is correct. It is more probable that the shell 

 had been stained by secondary oxide of iron . . ." 



Paramusium is synonymized here because the author feels that, 

 despite the anatomical distinctions of Amussium dalli (its type and only 

 species), the shell characters on which the unit was based ally it with 

 this genus. 



Pseudopalliorum Oyama was based primarily on the large anterior 

 auricle of the right valve of the type, Pecten interradiatus ; its other 

 features, however, correspond to Propeamussium, and in this case the 

 large auricle is of only specific importance. 



From the diagnoses of both Flavamussium and Luteamussium the 

 present author finds no justification for their existence as supraspecific 

 units ; the criteria on which they were based are again regarded as being 

 of only specific value. 



For the distinctions between Propeamussium and Parvamussium, see 

 Remarks under the latter. 



Propeamussium sensu lato comprises a large number of varied forms, 

 and is in need of much further study. In referring species to Prope- 

 amussium or Parz>a?nussium the author based his conclusions on the 

 species in his collection and the descriptions and figures of others cited 

 under either unit. Nearly all are deep-water species, many being known 

 by only one or several specimens. As more material becomes available, 

 the position of some species will undoubtedly need correction. 



Key to the eastern Pacific Species of Propeamussium 



1. With 9 internal lirae malpelonium (Dall) 



1. With 11-12 internal lirae . . meridionale (E. A. Smith) 



