80 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 23 



Pecten (Chlamys) jordani Arnold. Oldroyd, 1924a, p. 55, pi. 28, figs. 

 5, 6. "Puget Sound. In the Pliocene and Pleistocene of Santa 

 Barbara, San Pedro, and San Diego." 

 Pecten (Pecten) islandicus Miiller variety jordani Arnold. Grant & 

 Gale, 1931, p. 164, pi. 11, fig. 4. "U. Pliocene: Santa Barbara 

 (Arnold) ; upper Pico, Santa Barbara zone, Ventura Co. (Water- 

 fall). Pleistocene: Type locality; also in the lower San Pedro series 

 of the same locality (Arnold). Living: at various localities vv^ith 

 hindsit, not the specimen figured by Oldroyd (see Kincaidi) ." 

 Pecten (Pecten) islandicus Miiller variety kincaidi Oldroyd. Grant & 

 Gale, 1931, p. 164. "Living: In Puget Sound (and elsewhere with 

 hindsii'^) y 

 Pecten jordani Arnold. Eyerdam, 1938, p. 125. "Izhut Bay, Afognak 

 Island, Alaska. Former range : Puget Sound and Strait of Georgia. 

 Extended range: about 1200 miles northwestward." 

 Pecten (Chlamys) hindsii jordani Arnold. Proc. Conch. Club So. Calif., 

 1944, no. 35, p. 6. Pliocene of Deadman Island, San Pedro, Calif. 

 . . . Forrester Island, and Howkan, Alaska, and in Puget Sound 

 (Willett). [Eyerdam record also cited.] 

 Holotypc: U.S. National Museum. 



Type locality: Pleistocene of Deadman Island, San Pedro, Cali- 

 fornia. 



Original description: Shell of medium size, shape of P. hericeus, 

 inequivalve, rather thin ; right valve with twenty-five to thirty angular, 

 smooth-topped, imbricated ribs, which become dichotomous after reach- 

 ing a length of about 30 mm. ; interspaces deeply channeled and narrower 

 than ribs ; anterior ear imperfectly radially ribbed with six ridges, and 

 showing elevated, concentric, incremental lines; posterior ear nearly 

 obsolete, showing four ribs ; byssal notch not deep ; left valve shows 

 twenty-five to thirty narrow, convex ribs, showing imbrications only 

 slightly; interspaces as wide as ribs; after a diameter [altitude] of 30 

 mm. has been reached by the shell, small riblets appear in the widening 

 interspaces ; anterior ear shows five narrow, imbricated ridges, with wide 

 interspaces; both valves show a tendency to contract suddenly at the 

 basal margin upon nearing completion of growth ; surface of both valves 

 covered with a minute, lattice-like sculpture, which is generally worn 

 off on exposed portions of the shell. Dimensions. — Long. 42 mm. ; alt. 

 45 mm. ; diam. 15 mm. ; hinge 18 mm. 



Remarks: Arnold's criteria for Pecten (Chlamys) jordani are not 

 all stable features ; the ribs of the left valve are occasionally rather broad 

 and flattened, the imbricating sculpture (but not the reticulating) is 



