184 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
marked by numerous, slender, wavy, subequal and subequally closely 
spaced, spiral striations, of which about 33 occur upon the last turn between 
the summit and the periphery. Periphery of the last whorl marked by a 
slender raised keel, decidedly angulated. Base short, moderately rounded, 
narrowly attenuated anteriorly to re-enforce the columella, sculptured like 
the posterior portion of the whorls. Aperture ovate, very broad, slightly 
effuse anteriorly; posterior angle acute; columella very slender, evenly 
curved, closely appressed to the attenuated base, with a strong fold at its 
insertion which is barely visible when the aperture is viewed squarely. 
Length, 5.6; diameter, 2.8 mm. (Dali and Bartsch.) 
Type in United States National Museum, No. 150565. Type locality, 
Nanaimo, British Columbia. 
Range. Sitka, Alaska, to Port Harford, California. 
Odostomia atossa Dali, 1908 
Proceedings of the United States National Museum, 34:253; 52; PI. 26, fig. 8, 1909. 
Shell small, bulimiform, bluish-white, polished, with four gently convex 
whorls beside a very minute (and somewhat eroded) nucleus of about 
one whorl; suture distinct, not appressed; surface with two or three faint 
spiral threads on the second, four or more on the third, becoming obsolete 
on the last, subequally distributed between the sutures; besides these there 
are numerous extremely fine spiral striae only visible under a lens, and 
which become obsolete toward the aperture; aperture subovate, acute 
behind; outer lip simple, sharp; anterior margin gently rounding into the 
arcuate pillar lip, which has a single plait close to the body; a thin wash of 
transparent enamel on the body; axis imperforate; operculum thin. Height 
of shell 6.25; of last whorl, 5.0; of aperture, 3.25; maximum diameter, 
3.7 mm. (Dali.) 
Type in United States National Museum, No. 110637. Type locality, 
San Pedro, California. 
Range. Known only from type locality. 
Odostomia baldridgae Bartsch, 1912 
Proceedings of the United States National Museum, 42:284; PI. 38, figs. 1, la. 
Shell very elongate-conic, yellowish-white. Nuclear whorls small, im¬ 
mersed in the first of the succeeding turns, above which only half of the 
last volution projects. Post-nuclear whorls high between the sutures, 
appressed at the summit, slightly rounded, marked by feeble lines of 
growth, and many subequal and subequally spaced, strongly incised, spiral 
lines. About 25 of these occur between the sutures of the fourth whorl 
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