COMPLETE GRAU : PECTINIDAE OF THE EASTERN PACIFIC 17 



amussium, but its type, Amussium torresi, was very logically referred to 

 Parvamussium by Oyama ( 1944, p. 252). 



Xenamussium and Squaina?nussiurn of Oyama are synonymized be- 

 cause the present writer finds nothing in their diagnoses to separate them 

 from Parvamussium. Speaking of the type of the former, Pecten hos- 

 kynsi, Oyama (1951) said, "Whilst Pseudopallioruin is allied to Delec- 

 topecten, having internal lirae, this subgenus resembles Cyclopecten 

 Verrill as distinguished from the former." First, Delectopecten does not 

 have internal lirae ; second, Pecten hoskynsi almost always has them, al- 

 though Oyama did not mention them in his diagnosis of Xenamussium. 



As to Polynemamussium Habe, its type, Pecten intuscostatus, is only 

 specifically distinct from Propeamussium (Parvamussium) alaskense, a 

 representative species of Parvamussium. 



After his diagnosis of Bathyamussium Oyama (1951) said, "The 

 shape and sculpture is more like that of VariaTnussium, but the presence 

 of a byssal sinus suggests that it should be placed in Ctenamusium." 

 Actually, the byssal sinus of Amussium jejfreysii, the type of Bathy- 

 amussium, is almost obsolete, while that of A. cancellatum, the type of 

 Variamussium, is certainly more pronounced, even though not very deep. 



Micramussiufti was based on characters of only specific value, and 

 there seems to be nothing in its diagnosis to justify its existence as a 

 subgenus. 



In addition to the type, the following species are regarded by the 

 author as being referable to Parvamussium: the eastern Atlantic hos- 

 kynsi and fenestratu7Ji of Forbes, sublucidum and hypomeces of Daut- 

 zenberg & H. Fischer and lucidum Jeffreys; the western Atlantic 

 holmesii, sayanum, thalassinum and pourtalesianum of Dall and can- 

 cellatum E. A. Smith; the eastern Pacific alaskense and davidsoni of 

 Dall; the western Pacific ina, lacteum, zoniferum, texturatu?n, crista- 

 tellum and ?nargaritiferum of Dautzenberg & Bavay, jeffreysii, torresi 

 and squamigerum of E. A. Smith, thetidis and salcon of Iredale, sira- 

 tama and rubrotinctum of Oyama, cmadoritinctum Kuroda and intus- 

 costatum Yokoyama ; the Indian Ocean manaricum, solitarium and 

 investigatorium of E. A. Smith ; the Antarctic octodecim-liratum of 

 Melvill & Standen. 



See the last paragraph of Remarks under Propeamussium in regard 

 to the position of the above species. 



Key to the eastern Pacific Species of Parvamussium 



1. With internal lirae alaskense (Dall) 



1. Without internal lirae davidsoni (Dall) 



