254 University of California Publications in Zoology — [Vou. 14 
margins; base evenly rounded below; sides slightly concave above. Right valve 
with nine pairs of narrow, elevated, spiny ribs, along the sides of which are a 
pair of smaller spiny riblets; major interspaces much wider than ribs, concave- 
bottomed and ornamented by one or three thread-like, spiny, intercalary riblets; 
whole surface sculptured by microscopic imbricating lines, of which the spines 
on the ribs and riblets are only modifications; hinge line equal to one-half 
length of disk; ears unequal, the anterior being about two and one-half times 
the length of the posterior; anterior ear with seven or eight prominently spiny 
radials and minor riblets, and imbricating incremental lines; byssal notch deep 
and almost as wide as ear; posterior ear small, and sculptured by fine, spiny 
radials and imbricating incremental lines. Left valve with about nine narrow, 
very prominently spiny ribs; interspaces wide, concave-bottomed, and orna- 
mented by a single prominent, central imbricated riblet, on each side of which 
are minor thread-like riblets; whole surface of disk with fine incremental 
sculpture as in right valve; ears similar to those of right valve except that 
the anterior one has more ribs and riblets and no byssal notch. Hinge with 
almost obsolete cardinal erura. Color, golden yellow to pink, the left valve 
being the darker.’’ 
This species is occasionally found in the vicinity of San Francisco. 
It is not among the Survey collections. It is listed from this region 
by Wood and Raymond (1891). 
Range.—Puget Sound to San Pedro, California. 
Pecten latiauritus Conrad 
Pecten latiauritus Conrad (1837), p. 238, pl. 18, fig. 9; Arnold, R. (1903), 
p. 111, pl. 12, figs. 2 and 2a; Arnold (1906), p. 115, pl. 46, figs. 2, 2a, 
3, 3a. 
Description.—This species was described by Arnold (1906) as follows: 
“‘Shell averaging about 25 millimeters in altitude, about as long as high, 
inequivalve, compressed, inequilateral, disk obliquely produced posteriorly, thin; 
sides straight; margins smooth. Right valve more compressed than left, with 
12 to 16 low, rather squarish ribs, separated by equal, more or less distinctly 
channeled interspaces; whole surface sculptured by numerous fine concentric 
lines; hinge line nearly as long as disk; ears subequal in length; anterior ear 
long and narrow, with 5 or 6 prominent radials and numerous fine concentric 
lines; byssal notch deep and distinctly separating ear from disk; posterior ear 
from rectangularly to acutely pointed, sculptured by obsolete radials and con- 
centric lines. Left valve somewhat more convex than right, otherwise similar 
to it; anterior ear generally shorter and more prominently sculptured than 
posterior.’’ 
Length, 7 to 8 mm. 
Occurrence.—At stations D 5702 (1), D 5825 (1). 
Two immature specimens of Pecten that appear to belong to this 
species were dredged within the middle division of the bay. 
Range—San Francisco, Monterey to San Diego, California 
(Oreutt). 
