COMPLETE GRAU : PECTINIDAE OF THE EASTERN PACIFIC 43 



Cyclopecten (Delectopecten) polyleptus (Dall) 1908 



Plate 16, figs. 1-3 



Pecten (Pseuda?nusium) polyleptus Dall, 1908, p. 403, pi. 10, fig. 9. 



Holotypc. U.S. National Museum. 



Type locality: Albatross station 4642, four miles S, 41' E of Ripple 

 Point, Hood Island, Galapagos Islands, in 300 fathoms, globigerina 

 sand. [Dall gave the longitude as 41° E, obviously a mistake.] 



Original description: Shell small, thin, translucent vv^hite, com- 

 pressed, having a marked "Carnptonectes^' striation, besides about thirty- 

 six radial rows of minute, elevated, granule-like scales, very easily de- 

 tached and more crowded near the middle of the base; hinge line 

 straight ; anterior ear in the right valve long, prominent, with five radial 

 rows of scales and obvious concentric striation ; byssal notch deep and 

 wide, with a broad fasciole, the ctenolium with three free teeth ; posterior 

 ear not dififerentiated by a notch ; profile of the valve, below and behind, 

 a segment of a circle ; interior with glassy polish, scar small and high 

 up, hardly visible ; margins entire ; ligamentary pit small, shallow. Alt. 

 of valve, 9.5 ; Ion. of valve, 9.5 ; of hinge line, 6.5 ; diam. of right valve, 

 1.2 mm. 



Only the right valve was obtained at this station, but at station 2781, 

 on the west coast of Patagonia, Southern Chile, in South Lat. 51° 52', 

 in 348 fathoms, mud, ... a left valve which probably belongs to the same 

 species was dredged by the "Albatross" in 1888. The sculpture is es- 

 sentially similar, except that the scales are fewer and more distant from 

 each other ; only 34 rows could be counted, and the umbonal part of 

 the valve shows several concentric undulations. The ears are large, sub- 

 equal, the anterior larger with six radial rows of scales. The ^'Campto- 

 nectes^ sculpture is conspicuous upon the glassy shell. 



Remarks: Although similar to Cyclopecten Vancouver ensis, this 

 species differs greatly in sculpture. While C. vancouverensis has spinose 

 radial ridges, C. polyleptus has radial rows of scales, the ridges on the 

 former numbering twice as many as the rows of scales on the latter 

 (often more) ; C. vancouverensis has very minute, irregular, discon- 

 tinuous and rather divergent radial striae, C. polyleptus having fine but 

 more prominent radial ridges, which are only slightly irregular and are 

 continuous; the scales are also larger and more fluted in appearance 

 on C. polyleptus. 



