28 



ALLAN HANCOCK PACIFIC EXPEDITIONS 



VOL. 23 



material from the U.S. National Museum collection, and C. liriope was 

 found to be present from station 2807, near the Galapagos Islands, in 

 812 fathoms. 



Cyclopecten bistriatus (Dall) 1916 

 Plate 8, fig. 2 



Pseudamusium bistriatum Dall, 1916, p. 404. 



Pecten (Pseudamusium) bistriatum Dall. Dall, 1921, p. 20. [Original 

 record cited.] 



Holotype: U. S. National Museum. 



Type locality : U. S. Bureau of Fisheries, station 2923, off San 

 Diego, California, in 822 fathoms, green mud. 



Original description : Shell small, suborbicular, moderately convex, 

 white, thin ; left valve finely concentrically, rather distantly lamellose, 

 the lamellae closer and more conspicuous on the subequal ears; radial 

 sculpture of very fine, close-set, uniform almost microscopic elevated 

 lines, which do not reticulate the lamellations ; right valve with the con- 

 centric, but without the radial sculpture, concave near the margin, the 

 disk about as convex as the other valve, ears subequal, byssal notch short, 

 acute ; one or two faint radii on the ear above it. Height, 7 ; breadth, 7 ; 

 diameter, 2 mm. 



Additional descriptive notes: Dr. Harald A. Rehder, of the U. S. 

 National Museum, loaned the author three specimens from the type-lot; 

 two were still closed, but one had become separated, and it could then be 

 seen that the shell is actually translucent. The concentric ridges of the 

 left valve are stronger and more apparent than Dall's description indi- 

 cated. 



Geographical range: Santa Barbara Island, California, to Cape San 

 Lucas, Lower California, Mexico. Previously known only from the type 

 locality; in July, 1958, Dr. Rehder asked the author to identify 139 lots 

 of eastern Pacific material from the U. S. National Museum collection; 

 one lot contained specimens of Cyclopecten bistriatus from Albatross 

 station 2980, between Santa Barbara and San Nicolas Islands, Cali- 

 fornia, in 603 fathoms, green mud, and another lot contained specimens 

 from Albatross station 5683, off Cape San Lucas, Lower California, 

 Mexico, in 630 fathoms, green mud. Those records extend the northern 

 range by approximately 50 miles and the southern by approximately 

 880. 



