COMPLETE GRAU : PECTINIDAE OF THE EASTERN PACIFIC 37 



Cyclopecten barbarensis sp. nov. 



Plate 14, figs. 1-2 



Shell extremely small, quite thin, translucent, inequivalve and equi- 

 lateral, largest specimen found (a left valve) measuring 4.5 mm in 

 height ; hinge line about % as long as disk, w^ith beaks protruding slight- 

 ly above. Right valve shallowly convex and refllexed at ventral margin; 

 disk covered with numerous very fine concentric ridges, stronger near 

 ventral margin; 4-6 faint radial ridges adjoining anterior submargin. 

 Anterior auricle longer than posterior and with 9 lamellose radial rib- 

 lets; byssal notch rather shallow and no ctenolium present. Posterior 

 auricle with 6 lam.ellose radial riblets. Left valve rather deeply convex; 

 concentric sculpture consisting of 10 prominent rows of lamellae in 

 juvenile stage, increasing to 18-20 later; radial sculpture of low narrow 

 ridges, starting with 10-12 at the umbo and increasing by intercalation 

 to 24-32 (of varying strength) at the ventral margin. Anterior auricle 

 rather large and with shallow byssal sinus; rows of concentric lamellae 

 present as on disk, starting with 8-10 in juvenile stage and increasing 

 to 12-15; 7 or 8 fine radial ridges in juvenile stage, increasing to 10-12. 

 Posterior auricle with 5-7 rows of concentric lamellae in juvenile stage, 

 increasing to 8 or 9; 6 or 7 radial ridges, increasing to 8-10. External 

 sculpture clearly visible from interior of valve. 



Holotype: Juvenile specimen: height and length 3 mm; diameter 

 1 mm; hinge line 2.3 mm. Largest valve found (left): height and 

 length 4 mm; diameter 1.5 mm; hinge line 3 mm. Allan Hancock 

 Foundation. 



Type locality : Off Santa Barbara Island, southern California, in 27 

 fathoms, Hancock expeditions bottom sample 1064; 33° 30' 01" N; 

 1 19° 02' 20" W ; May 29, 1939. 



This species also occurred in bottom sample 1086, taken off the east 

 side of San Nicolas Island, southern California, in 30 fathoms; 33° 18' 

 20" N; 1 19° 28' 45" W. 



Re?narks: The sculpture of the left valve of this species separates it 

 from any other eastern Pacific Cyclopecten. In fact, of all the species of 

 this genus, the only one with similar concentric lamellae is the New 

 Zealand Cyclopecten aupouria Powell (1937, p. 167, pi. 47, figs. 1-2). 

 On the eastern Pacific C. incongruus (Dall) and the western Atlantic 

 C. reticulus (Dall) the lamellae are much less prominent. (The latter 

 species was described by Dall (1886, p. 221, pi. 5, figs. 8, 10) as Pecten 

 (Pseudamusium) reticulus.) 



