60 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
Type in U. S. N. M., No. 150233. Type locality, off Tillamook Bay, 
Oregon, Station 3346, in 786 fathoms. 
Range. Pribiloff Islands, Bering Sea, to San Diego, California. 
Pecten vancouverensis Whiteaves, 1893. 
Plate 12, figs. 6, 7. 
Ottawa Nat., 7 :133; pi. 1, fig. 1. 
Shell small, equivalved, compressed lenticularly, both valves being 
equally convex, ovately subcircular in outline apart from the ears and 
rather oblique; valves extremely thin and fragile, translucent and almost 
transparent, pale horn color with a slightly yellowish hue. Beaks placed 
a little behind the mid-length; hinge line straight and very long; ears 
unequal in size, the posterior pair, which are much smaller than the ante¬ 
rior, alike indistinctly defined, and merging gradually and imperceptibly 
into the general convexity and marginal contour of that side of each valve; 
anterior ears large, subtriangular, prolonged laterally, and longer than 
high, distinctly defined, that of the right valve with a deep and acutely 
angular byssal sinus at its base. Surface marked by densely crowded 
and exceedingly minute, irregular, and rarely continuous, but on the 
whole, radiating, simple or bifurcating raised lines, also by comparatively 
large, regularly disposed, and distant squamose radii. In the center of 
each valve the minute and nonsquamose raised lines are essentially parallel 
to the larger squamose radii, but on the sides the former are disposed 
obliquely to the latter. The surface of the anterior ear of each valve is 
minutely cancellated with extremely minute raised lines, which are almost 
parallel to the hinge line, in addition to the coarse cross lines. The whole 
sculpture of the exterior of the test is far too minute to be clearly seen 
without the aid of a miscroscope or powerful simple lens, but under either 
of these a few faint concentric lines of growth are also visible. Length, 
7.75; height, 7.5; diameter, 2.25 mm. (Whiteaves.) 
It was taken for the young of P. caurimis. 
Type in Ottawa? Type locality, Forward Inlet, Quatsino Sound, 
Vancouver Island. 
Range. Bering Sea to San Diego, California. 
Pecten bistriatus Dali, 1916. 
Proc. U. S. N. M., 52:404. 
Shell small, suborbicular, moderately convex, white, thin, left valve 
finely concentrically, rather distantly lamellose, the lamellae closer and 
more conspicuous on the subequal ears; radial sculpture of very fine, 
close-set, uniform almost microscopic elevated lines, which do not reticu¬ 
late the lamellations; right valve with the concentric, but without the 
radial sculpture, convex near the margin, the disk about as convex as the 
