88 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
Alvania aurivillii Dali, 1886 
Plate 80, fig. 5 
Proceedings of the United States National Museum , 9:308; PI. 4, fig. 8. 
Shell elongate-conic, thin, fight yellow. Nuclear whorls one and one- 
half, strongly rounded, smooth. Post-nuclear whorls rounded, shouldered 
at the summit, marked by two, strong, spiral keels, between the sutures, 
on the first two turns; the first keel being on the middle and the second a 
little posterior to the suture; the space between the summit and the first 
keel slopes regularly. Beginning with the third whorl a third keel appears, 
and the space between the sutures is here divided into four parts, of which 
the one at the summit is a little broader than the rest. On the last turn the 
peripheral keel is completely shown in the suture, and a slender, spiral 
thread appears immediately below the summit. The spaces between the 
keels are about four times as wide as the keels. Suture quite strongly con¬ 
stricted. Periphery of the last whorl marked by a strong, spiral keel which 
is a trifle nearer to the first keel posterior to it than that is to its neighbor. 
Base moderately long, well-rounded, narrowly umbilicated, marked by 
three equal and almost equally spaced spiral keels. In addition to the spiral 
sculpture, the whorls are marked by numerous, very slender, raised, axial 
threads, which are best developed in the broad spaces between the spiral 
keels. Aperture subcircular, slightly expanded anteriorly; posterior angle 
obtuse; outer lip thin, showing the external sculpture within; inner lip 
strongly curved, somewhat reflected; parietal wall covered with a thick 
callus, which joins the posterior angle to the columella and renders the 
peritreme complete; operculum thin, corneous. Length, 4.2; diameter, 
2.0 mm. (Dali.) 
Type in United States National Museum, No. 213680. Type locality, 
Adakh Island, Alaska. 
Range. Kyska to Adakh Island, Aleutians. 
Alvania bakeri Bartsch, 1910 
Plate 80, fig. 2 
Nautilus, 23:137; PI. 11, fig. 8. 
Shell minute, bluish-white. Nuclear whorls one and one-third, form¬ 
ing a moderately elevated spire. Upper half of the well-rounded nuclear 
whorls marked by about ten, very fine, closely spaced, spiral striations; 
lower half marked by numerous, closely spaced, depressed, elongate 
granules, each of which has the long axis decidedly protractively slanted, 
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