CLASS GASTROPODA 
173 
posterior keel forms the strong tabulation at the summit of the whorls 
and is strongly tuberculated, fourteen tubercles appearing upon the second 
and twenty upon the remaining whorls. The space between the keels is 
marked by rather strong lines of growth. The greatest convexity coincides 
with the superperipheral keel. Aperture irregularly ovate, somewhat effuse 
anteriorly; posterior angle obtuse; outer lip angulated by the keels, thin, 
showing the external markings within; columella strong, curved, without 
visible fold in the aperture; re-enforced by the base; parietal wall covered 
by a thin callus. Length, 1.9; diameter, 0.9 mm. (Dali and Bartsch.) 
Type in United States National Museum, No. 129335. Type locality, 
San Pedro, California. 
Range. San Pedro, California, to Cape San Lucas, Lower California. 
Odostomia hemphilli Dali and Bartsch, 1909 
Bulletin 68, United States National Museum, 176; PI. 19, fig. 10. 
Shell broadly conic, milk-white. Nuclear whorls deeply obliquely 
immersed, apparently smooth. Post-nuclear whorls well-rounded, marked 
with three, strong, equal spiral keels, the posterior two of which are 
tuberculate, the third one smooth. The tubercles are connected axially by 
slender riblets, which extend to the third keel. There are about twenty 
tubercles on the latter whorls, while on the early whorls they are ill-defined. 
Sutures deeply channeled. Periphery of the last whorl marked by a 
smooth spiral keel, equal to the one posterior to it. Base moderately 
long, well-rounded, marked by four spiral keels, which grow successively 
weaker anteriorly. Aperture irregularly ovate; posterior angle obtuse; 
outer lip thin, showing the external sculpture within; columella stout, 
provided with a strong fold at its insertion. Length, 3.5; diameter, 
1.4 mm. (Dali and Bartsch.) 
Type in United States National Museum, No. 162841. Type locality, 
San Iiipolito Point, Lower California. 
Range. San Pedro, California, to Point Abreojos, Lower California. 
Subgenus Ivara Dali and Bartsch, 1903 
Odostomia terricula Dali and Bartsch, 1903 
Memoirs of the California Academy of Sciences, 3: 285; PI. 4, fig. 14, 1903. 
Shell very elongate-ovate, milk-white. Nuclear whorls smooth, 
obliquely immersed in the first of the succeeding turns, above which only 
the tilted edge of the last volution projects. Post-nuclear whorls moder¬ 
ately rounded, very broadly tabulately shouldered at the summit, moder- 
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