98 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
spaces between the sutures into four almost equal portions. The intersec¬ 
tion of the spiral cords and the axial ribs form strong tubercles, while the 
spaces inclosed between them are well impressed, rectangular pits, having 
their long axes parallel with the spiral sculpture. Suture strongly con¬ 
stricted. Periphery of the last whorl marked by a spiral sulcus equal to 
that which separates the supraperipheral spiral cord from its posterior 
neighbor and, like it, is crossed by the continuations of the axial ribs, 
which extend over the first two basal spiral cords and render them tu- 
berculate. Base well-rounded, rather short, produced anteriorly, marked 
by three strong sublamellar, spiral cords which are about one-third as 
wide as the spaces that separate them. Aperture very oblique, twisted, 
ovate; posterior angle obtuse; outer lip thickened at the edge within the 
lip, re-enforced behind the edge by a strong varix, inner lip very stout, 
strongly curved, and appressed to the base; parietal wall covered with a 
very thick callus, which renders the peritreme complete. 
Type in (not known to writer). Cotypes, United States National Mu¬ 
seum, No. 219564. Type locality, San Diego, California. 
Range. Catalina Island, California, to Todos Santos Bay, Lower Cali¬ 
fornia. 
Alvania oldroydae Bartsch, 1911 
Plate 81, fig. 3 
Proceedings of the United States National Museum, 41:360; PI. 32, fig. 3. 
Shell minute, broadly ovate, yellowish white. Nuclear whorls one and 
one-half, well-rounded, smooth. Post-nuclear whorls inflated, weakly 
shouldered on the posterior fourth between the sutures, marked by nu¬ 
merous slender, rather closely spaced, well-rounded, slightly protractive 
axial ribs, of which 20 occur upon the first, 24 upon the second, and 28 
upon the penultimate whorl. In addition to the axial sculpture, the whorls 
are marked by slender spiral threads, which are almost equal to the axial 
ribs. Of these threads, three occur upon the first and second whorl, divid¬ 
ing the space between the sutures into four almost equal portions, the space 
at the summit being a little wider than the rest; the first spiral thread 
marks the termination of the sloping shoulder. On the penultimate whorl 
an additional spiral cord makes its appearance in the space immediately 
below the summit, a little nearer to the summit than the first spiral cord 
on the previous whorl. The intersections of the axial ribs and the spiral 
cords form slender rounded tubercles. The spaces inclosed between the 
three cords on the early whorls and the same on the last turn are squarish 
pits, while the spaces between the summit and the first spiral cord and the 
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