10 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
adult shell becomes reduced to mere rounded angles; interstitial riblets 
wanting, or with one or two low cords developed in each interval toward 
the larger end of the shell only; usually with coarse wrinkles of growth 
on the larger half of the length. Aperture hexagonal, but with the angles 
so rounded as to appear almost circular; oblique; anal orifice rounded- 
oval, without notch or slit. Length, 30.5; diameter of aperture, 2.5 mm. 
(Sharp and Pilsbry.) 
Type in Philadelphia Academy of Sciences. Type locality, Santa 
Barbara, California. 
Range. Monterey, California, to Guacomayo, Central America. 
This species has been called D. hexagomim Gould by California collec¬ 
tors. 
Dentalium semipolitum Broderip and Sowerby, 1829 
Zoological Journal, 4:369. Tryon and Pilsbry, Manual of Conchology, 17; PI. 16, 
fig. 54. 
Shell slender, moderately or decidedly curved, attenuated toward the 
apex; rather thin, milk-white and very glossy. Sculpture: deeply engraved 
with very numerous, fine, close, subequal, longitudinal striae, extending 
from the apex downward one-third to two-thirds the shell’s length (and of 
course covering the entire length of young shells) ; the remaining one- or 
two-thirds smooth and polished, brilliant, scarcely showing growth-lines. 
Aperture circular, the peristome thin; anal orifice minute and round, no 
notch or slit. Length, 26; diameter, of aperture, 2.6 mm. (Tryon and 
Pilsbry, Manual of Conchology .) 
Type in British Museum. Type locality, not specified. 
Range. San Pedro, California, to La Paz, Lower California. 
Dentalium dalli Pilsbry and Sharp, 1897 
Plate 1, fig. 5 
Tryon and Pilsbry, Manual of Conchology, 17; PI. 21, fig. 46. 
Shell regularly but only slightly curved, evenly tapering, thin and 
fragile; opaque, slightly bluish-white. Surface brilliant, glossy, and pol¬ 
ished ; but, in all specimens seen, mainly dead or lusterless whitish from 
loss of the greater part of the superficial gloss, which remains near the 
aperture only, or sometimes in patches or irregular rings elsewhere. 
Growth-striae faint; no other sculpture. Aperture circular, thin-edged 
orifice; no slit or notch. Length, 45; diameter of aperture, 4; at apex, 
1.5 mm. (type). (Pilsbry and Sharp.) 
Type in United States National Museum, No. 107696. Type locality, 
Bering Sea. 
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