50 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 23 



Regarding Pseudamussium gelatinosum Mabille & Rochebrune, Dall 

 (1908, p. 404) said, "This is the species which by some authors has been 

 referred to P. vitreus Gmelin, from which it differs by sparser distribu- 

 tion of the scales and of the rows of scales, and by a slight but obvious 

 obliquity. The two forms are, however, extremely similar." For the 

 following reasons the present author has synonymized Pseudamussium 

 gelatinosum with Cyclopecten vitreus. First, nothing in its original 

 description separates it from C. vitreus'', second, Dall's criteria for separa- 

 tion are features fairly common to the typical ; third, through the kind- 

 ness of Dr. Harald A. Rehder, of the U.S. National Museum, the 

 author's collection contains three specimens from the lot on which Dall 

 based his opinion {Albatross station 2785, cited above), and they are 

 identical with specimens in series of C. vitreus from various localities. 



Geographical range'. Eastern Atlantic: Iceland, western Norway, 

 Shetland Islands, southwestern France, northern Spain, Portugal, 

 Azores, Canary Islands, Cape Verde Islands, and off northwestern Afri- 

 ca. Mediterranean. Western Atlantic: Greenland to Chesapeake Bay; 

 western Florida ; Santa Cruz Territory, Argentina, to Strait of Magel- 

 lan. Eastern Pacific: Strait of Magellan to 49° N (off southern Chile) ; 

 Clipperton Island (670 miles SW of Acapulco, Mexico). Western 

 Pacific: Moluccas; Philippine Islands; Japan (to 35° N). 



This is the most widely distributed species of Pectinidae. Clipperton 

 Island is added here, since the author determined specimens from there 

 referred to Cyclopecten zacae Hertlein to be C. vitreus. 



G eochronological range : Pliocene, Pleistocene, Recent. 



Bathymetric range: Recorded in 15 to 2327 fathoms. 



Ecological data: From the little available, usually found on mud 

 bottoms ; often attached to gorgonians or hydroids ; Japanese specimens 

 frequently living on the giant crab, Macrocheira kaempferi De Haan. 



Cyclopecten (Delectopecten) zacae (Hertlein) 1935 



Plate 19 



Pecten (Pseudajnusium) panamensis Dall, 1908, p. 404, pi. 6, figs. 8, 

 10. "U.S.S. "Albatross," station 3354, Gulf of Panama, in 322 

 fathoms, mud, bottom temperature 56° F. . . . Also at stations 

 3389, 3396, 3407, and 3422, ranging from near Acapulco, Mexico, 

 to the Galapagos Islands, in 141 to 885 fathoms, soft bottom, tem- 

 peratures 37.2° to 53.5° F." 



{non] Pecten panamensis Dall, 1898, p. 696. [== Pseudamussium (Pep- 

 lum) fasciculatmn (Hinds), 1845. See that species, this paper.] 



