COMPLETE GRAU : PECTINIDAE OF THE EASTERN PACIFIC 51 



Pecten (Delectopecten) zacae Hertlein, 1935, p. 321, pi. 18, figs. 3-6, 

 9-10, ". . . about 10 miles due east of San Jose del Cabo, [eastern] 

 Lower California, in 20 to 220 fathoms, ... ; ... off Cape San 

 Lucas, Lower California, in 20 to 25 fathoms." 

 Pseudamusium panamensis Dall, M. Smith, 1944, p. 52, fig. 687 [re- 

 production of original figures]. 

 [non] Delectopecten zacae Hertlein. Hertlein & Emerson, 1953, p. 350, 

 pi. 27, figs. 7, 10, 16. "110-200 fathoms off east slope of Clipperton 

 Island." [670 miles SW of Acapulco, Mexico; = Cyclopecten 

 (Delectopecten) vitreus (Gmelin).] 

 Holotypex U. S. National Museum. 



Type locality: Albatross station 3354, Gulf of Panama, in 322 

 fathoms. 



Original description: Shell translucent yellowish white, very thin, 

 resembling mica in consistency, oblique, compressed; beaks small, low, 

 polished, hardly projecting beyond the hinge line; ears small, subequal, 

 the posterior feebly differentiated; the anterior right ear with a wide 

 fasciole corresponding to the byssal sulcus, above which are five or more 

 radial threads, the whole with strong incremental lines; on the lower 

 margin of the fasciole is a line of minute beads, apparently a ctenolium 

 which becomes obsolete at maturity; the other ears are sculptured like 

 the rest of the disk; sculpture: on the left valve a feeble but distinct 

 "'Camptonectes^ striation, rather coarse and irregular incremental lines, 

 the whole crossed by 40-65 fine radial, sparsely, minutely scaly threads, 

 the scales occurring usually at the intersection with a prominent incre- 

 mental line; left [lapsus calami: right] valve with similar sculpture 

 except that the ''Camptonectes' striation is so fine as to require strong 

 magnification and a good light to be seen at all ; the valves are produced 

 obliquely downward and backward; the surface sculpture yields readily 

 to friction and many of the valves have lost it altogether, retaining only 

 the concentric sculpture ; left valve slightly more convex ; interior glassy, 

 the resiliary pit very small, the margins entire. Height, 18; length, 18; 

 max. diam. 2.5 ; hinge line, 9.5 mm. A very large specimen is 22 mm. 

 high. 



Additional descriptive notes: Specimens from the Gulf of California 

 are more convex, smoother and glossier than those from the Gulf of 

 Panama, and often have a few very faint concentric undulations of the 

 disks below the umbonal region. Dall was correct in surmising that the 

 "minute beads on the lower margin of the fasciole" comprise a ctenolium 

 in the juvenile stage; the teeth become bead-like after the shell reaches 



