204 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
by the base, provided with a fold at its insertion. Length, 4.9; diameter, 
2.7 mm. (Dali and Bartsch.) 
Type in United States National Museum, No. 56770. Type locality, 
Santa Rosa Island, California. 
Range. Known only from type locality. 
Odostomia serilla Dali and Bartsch, 1909 
Bulletin 68, United States National Museum, 209; PI. 24, fig. 9. 
Shell elongate-conic, white. Nuclear whorls deeply obliquely immersed 
in the first of the succeeding turns, above which only the tilted edge of the 
last volution projects. Post-nuclear whorls well-rounded, rather high 
between the sutures, contracted at the periphery, strongly, narrowly tabu- 
lately shouldered at the summit. Suture strongly marked. Periphery of 
the last whorl and the rather long base well-rounded. Entire surface of 
spire and base marked by numerous lines of growth and well-incised spiral 
striations. Aperture ovate, posterior angle acute; outer lip thin; columella 
strongly curved, slightly revolute, provided with a fold at its insertion. 
Length, 4.8; diameter, 2 mm. (Dali and Bartsch.) 
Type in United States National Museum, No. 206917. Type locality, 
University of California Station 59, off San Diego, California. 
Range. Known only from type locality. 
Odostomia septentrionalis Dali and Bartsch, 1909 
Bulletin 68, United States National Museum, 200; PI. 26, fig. 9. 
Shell very elongate, ovate, thin, umbilicated, soiled yellowish-white. 
Nuclear whorls small, smooth, very obliquely, deeply immersed in the first 
of the succeeding turns. Post-nuclear whorls inflated, well-rounded, 
summits appressed, marked by fine, retractive lines of growth and 
numerous fine, wavy, spiral striations between the sutures and on the base. 
The posterior half of the base has, in addition to the above markings, three 
broad, low, feeble, raised, spiral threads. Umbilicus very narrow. Aper¬ 
ture large, very regularly oval; posterior angle obtuse, the thin outer lip 
bending strongly outward in a broad sweeping curve; columella long, 
slender, regularly curved and moderately reflected, not re-enforced by the 
base; provided with a feeble oblique fold at its insertion; parietal wall 
glazed with a thin callus. Length, 4.3; diameter, 2.7 mm. (Dali and 
Bartsch.) 
Type in United States National Museum, No. 159462. Type locality, 
Unalaska, Alaska. 
Range. Known only from type locality. 
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