COMPLETE GRAU : PECTINIDAE OF THE EASTERN PACIFIC 31 



ture of the ears is very similar, but the lines are less close and sharp and 

 the anterior auricle has a deep triangular byssal sulcus, without a notice- 

 able fasciole or a ctenolium ; left valve with the umbo sharp, small, and 

 prominent, the disk nearly smooth, with faint radial striae which near 

 the submargins become more regular and sharp, especially behind ; right 

 valve with a less prominent umbo, the surface polished, the ventral 

 margin flexible, and reflexed when closed ; sculpture of fine, close, regular 

 concentric lines with wider flat interspaces; interior smooth, polished, 

 without radial lirae; the hinge line with two well-marked transversely 

 striated provincular areas. Height of shell, 8.7 ; breadth, 9.0 ; hinge line, 

 5,0 ; diam. 2.0 mm. 



The faint white rays on the right valve of this shell look so much 

 like Propeamusium that until I separated the valves of one of the speci- 

 mens I had no doubt it belonged to that group. 



Additional descriptive note: Dall failed to mention a very distinctive 

 feature of this species: the shallow concave fold of the posterior portion 

 of the left valve, extending from the umbo to the ventral margin. His 

 figure 1, a drawing, shows this feature, although somewhat exaggerated. 

 Cyclopecten exquisitus sp. nov., described in this paper, is the only other 

 species of this genus in which the left valve is similarly flattened. 



Geographical range: Reported only from the type locality and from 

 Albatross station 2794, Gulf of Panama (off Punta Mala), in 62 

 fathoms. Incidentally, Dall gave as the type locality "Cocos Island, 

 Gulf of Panama." Cocos Island is actually over 400 miles west (slightly 

 southwest) of the Gulf. 



Cyclopecten acutus sp. nov. 

 Plate 10, fig. 2 



Shell very small, rather thin but opaque, glossy, slightly inequivalve 

 and equilateral, largest specimen found (a left valve) measuring 4 mm 

 in height; hinge line usually same length as disk but occasionally some- 

 what shorter; beaks protruding slightly. Right valve moderately convex 

 (slightly less than left valve) and covered by a thin transparent layer of 

 shell extending beyond entire margin of valve except in center of hinge 

 margin ; only sculpture on disk consisting of extremely faint concentric 

 ridges. Anterior auricle very slightly longer than posterior and with 

 numerous fine concentric lamellae; byssal notch rather shallow and no 

 ctenolium. Posterior auricle pointed and finely concentrically lamellose. 

 Left valve moderately convex and covered by same transparent layer of 



