CLASS GASTROPODA 
175 
Subgenus Iolaea A. Adams, 1867 
Odostomia amianta Dali and Bartsch, 1907 
Plate 57, figs. 9, 9 a 
Proceedings of the United States National Museum, 33:519; PI. 46, fig. 9. 
Shell broadly conic, yellowish-white. Nucleus small, of two whorls, 
which increase extremely rapidly in size and are obliquely placed. Post- 
nuclear whorls very strongly shouldered, marked by three, very strong, 
lamellar, spiral keels on the first and second, and four on the succeeding 
whorls between the sutures. The posterior keel marks the limit of the 
broad, sloping shoulder and is much the strongest. It is also placed a 
little farther apart from the next spiral keel than that is from its neighbor. 
Base of the last whorl well-rounded; ornamented by eight spiral ridges, 
which are less elevated and much more closely and regularly spaced than 
those between the sutures. The peripheral groove is about equal in width 
to the one anterior to the posterior keel. The entire shell is marked by 
fine, sublamellar, regularly spaced, retractive, axial ribs, which render the 
spiral keels somewhat crenulated at their meeting points and break the 
spaces between them into small squares or oblongs. These riblets extend 
from the sutures to the small umbilicus. Aperture subovate, posterior angle 
obtuse; outer lip thin, somewhat wavy, showing the external sculpture 
within; columella moderately stout, somewhat curved, and strongly revo¬ 
lute, having an oblique fold near its insertion which is barely visible when 
the aperture is viewed squarely; parietal wall covered by a fairly thick 
callus. Length, 4.4; diameter, 2.3 mm. (Dali and Bartsch.) 
Type in United States National Museum, No. 105483. Type locality, 
Point Abreojos, Lower California. 
Range. Monterey Bay, California, to Point Abreojos, Lower Cali¬ 
fornia. 
Odostomia eucosmia Dali and Bartsch, 1909 
Bulletin 68, United States National Museum, 183; PI. 20, fig. 10. 
Shell elongate-conic, subdiaphanous to milk-white. Nuclear whorls 
deeply obliquely immersed in the first of the succeeding turns, above which 
only the tilted edge of the last one projects. Post-nuclear whorls some¬ 
what contracted at the periphery, very strongly slopingly shouldered at 
the summit, marked by three strong lamellar keels between the sutures, 
of which the middle one is a little nearer to its anterior neighbor than to 
the posterior, the latter being about as far from the summit as it is from 
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