CLASS PELECYPODA 
75 
Modiolaria protracta Dali, 1916. 
Plate 3, fig. 2. 
Proc. U. S. N. M., 52 :405. 
Shell resembling the young of typical form but more inflated and 
elongated, the sculpture very distinct, the medial area smooth, blackish, 
the dorsal areas olivaceous. Length, 13; height, 6.5; diameter, 5.5 mm. 
(Dali.) 
Type in U. S. N. M., No. 222017. Type locality, north of Nunivak 
Island, Bering Sea, in 9 fathoms gravel. 
Range. Nunivak Island, Bering Sea, to Monterey, California. 
Modiolaria olivacea Dali, 1916. 
Proc. U. S. N. M., 52:405. 
Shell small, thin, polished, pale olivaceous near the beaks, growing 
darker distally; medial area smooth, anterior area with six or seven rather 
strong radial grooves; posterior area with numerous, shallow-channeled 
radii crossed by rather regular, slightly elevated concentric lines, giving 
a silky luster to the surface; beaks inconspicuous, inflated; dorsum arched, 
base nearly straight, both ends evenly rounded, the posterior slightly 
wider; interior whitish, the margin crenulated by the sculpture, the beaks 
very close to the posterior end. Length, 10; height, 6; diameter, 6 mm. 
(Dali.) 
Type in U. S. N. M., No. 210790. Type locality, off Bering Island, 
in 10 fathoms. 
Range. Bering Sea to Catalina Island, California. 
Modiolaria impressa Dali, 1907. 
Plate 11, figs. 4, 5. 
Smithsonian Misc . Coll , 50:172. U. S. N. M. Bull , 112; pi. 3, figs. 6, 7. 
Shell small, thin, arcuate, elongate, olive-green or brownish, with a 
small striate anterior area, deeply impressed middle area and large, tumid, 
nearly smooth posterior area; surface polished, beaks very anterior, incon¬ 
spicuous; anterior area very short, with about six pairs of strong radial 
riblets; middle area polished, smooth, gaping below for the byssus, where 
the margin is a little convex, behind which it is conspicuously excavated; 
posterior area swollen, arcuate above, produced behind and below, drop¬ 
ping vertically to meet the depressed middle area, faintly concentrically 
and obsoletely minutely radiately striated; interior pearly; inner margins 
crenulate around the distal areas, medially smooth, with a few interlocking 
denticulations just behind the internal ligament, but none in front of the 
beaks; byssus strong. Length, 10; height, 19; diameter, 9 mm. (Dali.) 
