110 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL.23 



specimen of C. latiaurata. Dall's label reads: "Pecten tumbezensis (-|- 

 aspersus Sby.) Orb. = P. sowerbyi Reeve, Thesaurus [sic] f. 4, 1852; 

 very close to P. latiauritus Conr." Arnold's phrase, "A pair of valves," 

 is misleading; the valves are now separated but match perfectly. How- 

 ever, it is very doubtful that the animal was still alive when the shell 

 was taken (even though it may still have been attached to the valves), for 

 the specimen was found in green mud at a depth of 276 fathoms; no 

 other specimen has been recorded living in the green mud so common to 

 deep water stations off the southern California coast, nor has any been 

 recorded from even half that depth. No doubt the animal died and the 

 valves, still attached, drifted or were carried to deeper water. 



This species differs from its subspecies monotimeris in having a 

 thicker shell, longer hinge line, acutely pointed auricles, less pronounced 

 obliquity, higher and narrower ribs, and concentric lamellae on the 

 disks. 



Geographical range: Point Reyes, California (38° N), to Cape San 

 Lucas, Lower California, Mexico, and north to Espiritu Santo Island 

 in the Gulf of California; Guadalupe Island, Mexico (180 miles west 

 of central Lower California). Previously this species had been found as 

 far south as Cape San Lucas but not in the Gulf; had Mrs. Oldroyd 

 said "to but not in the Gulf of California" her statement would have 

 been correct at the time it was written. The Hancock expeditions took 

 specimens of latiaurata in bottom sample 2197, in 6 fathoms off San 

 Gabriel Bay, Espiritu Santo Island, thus establishing for the first time 

 its presence in the Gulf; the location is about 125 miles north of the 

 mouth of the Gulf. 



Geochronological range: Pliocene, Pleistocene, Recent. 



Bathymetric range: Recorded in 1 foot (minus tide) to 125 fathoms. 



Ecological data : Found attached to rocks or pilings in shallow water ; 

 in deeper water on rock, shale, gravel or sand bottoms, often attached to 

 calcareous algae. 



Hancock Expeditions Collecting Stations: 

 SOUTHERN CALIFORNIA— 71 stations; 3-80 fathoms, rock, 



gravel, sand. 

 GULF OF CALIFORNIA— bottom sample 2197, 6 fathoms. 



Ghlamys (Leptopecten) latiaurata monotimeris (Conrad) 1837 



Plate 35, fig. 2 



Pecten Monotimeris Conrad, 1837, p. 238, pi. 18, fig. 10. "Inhabits 

 with the preceding [P. latiauratus Conrad]." ". . . below the efflux 

 of the tide near Sta. Diego and Sta. Barbara." 



