COMPLETE GRAU : PECTINIDAE OF THE EASTERN PACIFIC 25 



Type locality: Challenger station 310, off southern Chile, in 400 

 fathoms, blue mud; 51° 27' 30" S, 74° 3' W. 



Original description: Testa compressa, tenuissima, vitrea, nitida, 

 aliquanto inaequivalvis ; valva sinistra paulo convexior, fere laevis, striis 

 paucis concentricis aliisque radiantibus sculpta; valva dextra striis con- 

 centricis regularibus ornata. Auriculae inaequales, bene definitae, anticis 

 paulo majoribus, ilia valvae dextrae radiatim lirata, mediocriter profunde 

 sinuata. Margo valvae infra sinum rectilinearis, baud denticulatus. 



Length 7 mm., height 7V2, diameter 2. 



Additional description: Shell small, moderately compressed, trans- 

 lucent, shining and inequivalve. Sharp umbonal ridge from beak to point 

 where submargin meets ventral margin. Left valve moderately convex, 

 with distant concentric and radial striae. Right valve with more pro- 

 nounced concentric striae. Auricles unequal, distinct, anterior ones larger. 

 On right valve anterior auricle has a few radiating lirae, posterior 

 auricle with moderately deep byssal notch and with concentric striae. 

 Faint concentric striae on both auricles of left valve. 



Remarks: Known only from the type locality. 



Gyclopecten zephyrus sp. nov. 

 Plate 7, figs. 1-3 



Shell small, extremely thin, translucent, inequivalve and equilateral, 

 adult specimens averaging 8 mm in height and length; hinge line more 

 than half as long as disk, with beaks protruding slightly above. Right 

 valve moderately convex, with ventral ^ of disk thinner and reflexed; 

 55 to 75 fine concentric ridges covering disk, with very minute and ir- 

 regular radial striae between them; extremely thin outer layer of shell 

 present on some specimens, but apparently always worn ofif to some ex- 

 tent; anterior auricle moderately large and longer than posterior, with 

 fine concentric ridges; lower half of auricle with convex fold; byssal 

 notch shallow and no ctenolium present; posterior auricle with nearly 

 perpendicular lateral margin, and very finely sculptured by continuations 

 of discal ridges. Left valve more convex than right, and occasionally 

 with one or two faint concentric folds in umbonal area ; very fine and 

 widely spaced concentric ridges and slightly stronger and irregular radial 

 ridges often present on upper Yz to 1/4 of disk; auricles of same length 

 as those of right valve, and both with fine concentric ridges. 



Holotype: 9 mm in height and length; diameter 1.75 mm; hinge 

 line 5 mm ; Allan Hancock Foundation. 



