156 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
penultimate turn. The axial series slants retractively from the posterior 
suture. Sutures deep and broad, considerably wider than the spaces 
between the keels. Periphery of the last whorl deeply channeled, the 
channel marked by a weak extension of the axial bars which terminate 
at the first supraperipheral keel. Base prolonged, well-rounded, marked 
by seven strong, moderately-raised, spiral keels which, like the channels 
that separate them, diminish regularly in width from the periphery to the 
umbilical area; the last, the eighth, immediately behind the columella, being 
less distinct and considerably broader than the rest. The channels between 
the keels are about equal to the keels in width and are crossed by numerous 
very slender raised threads, which extend up on the sides of the keels 
but do not cross them. About five of these threads fall in the space 
between two tubercles on the spire, in the first supraperipheral groove. 
Aperture oval, large, effuse anteriorly, posterior angle obtuse, outer lip 
rather thick, not showing the external sculpture within; columella some¬ 
what twisted, revolute anteriorly, re-enforced by the attenuated base, and 
provided with a weak fold at its insertion ; parietal wall covered by a callus, 
which joins the columella with the posterior angle of the aperture and 
renders the peristome almost complete. Length, 3.1; diameter, 1.4 mm. 
(Dali and Bartsch.) 
Type in United States National Museum, No. 162771. Type locality, 
Monterey, California. 
Range. Known only from type locality. 
Odostomia cincta Carpenter, 1864 
Plate 58, figs. 2, 2 a 
Supplementary Report, British Association for the Advancement of Science, 659. 
Bulletin 68, United States National Museum, 152; PI. 15, figs. 2, 2a. 
Passing toward Miimiola. Radiating sculpture very faint. (Carpenter.) 
Shell elongate-ovate, vitreous. Nuclear whorls smooth, deeply immersed 
in the first of the succeeding turns, above which only the tilted edge of 
the last volution projects. Post-nuclear whorls well-rounded, marked by 
vertical axial ribs, which are strongest near the summit, becoming much 
enfeebled as they pass to the! suture. Of these ribs eighteen occur upon 
the second and third and twenty upon the fourth whorl. In addition to 
the ribs the whorls are marked by four, broad, strong, spiral keels which 
form nodules at their junction with the ribs. On the last whorl, the axial 
sculpture is obsolete on the anterior half between the sutures. Sutures 
subchanneled. Periphery of the last whorl marked by a strong keel. 
Base well-rounded posteriorly, effuse anteriorly, marked by six low, spiral 
cords, the two nearest the umbilical area being very faint. Aperture 
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