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3 30 American Seashells
I to 1% inches in length. Primary ribs i6 to i8, fairly distinct in
the young stages; sculptureless in the senile stage. Round in cross-section.
Chalky-white when eroded. Common from 20 to 1,000 fathoms.
Dentalium autillarum Orbigny Antillean Tusk
South half of Florida and the West Indies.
About I inch in length, roundish in cross-section. Primary ribs 9, but
increasing to 1 2 near the middle and finally with 24 near the aperture. Mi-
croscopic, transverse lines between the ribs. Color opaque-white, rarely
reflecting a greenish tint. Encircled with weak, zigzag bands or splotches
of translucent gray.
Dentalium pilsbryi Rehder Pilsbry's Tusk
West Florida and Brazil only.
Figure 69d
% to 1% inches in length, roundish in cross-section. Primary ribs 9,
with a smaller, weaker, rounded, secondary rib appearing between each. All
ribs fade out toward the anterior end. Intercostal spaces flat, crossed by
coarse growth lines. No transverse, microscopic sculpture. Color opaque-
white; without gray splotches. Formerly known as D. pseiidohexagonum
Henderson 1920, not Arnold 1903. Uncommon from 2 to 5 fathoms.
Dentalium pretiosum Sowerby Indian Money Tusk
Alaska to Lower California.
Figure 6gi
About 2 inches in length, moderately curved and solid; opaque-white,
ivory-like, commonly with faint dirty-buff rings of growth. Apex with a
short notch on the convex side. A common offshore species which was used
extensively by the northwest Indians for money.
Subgenus Fissidentalium Fischer 1895
Dentalium floridense Henderson Florida Tusk
Southeast Florida and the West Indies.
2 to 3 inches in length, roundish in cross-section. Shell hard and yel-
lowish white. Apex hexagonal with concave spaces between. Ribs increase
to 24 anteriorly and are rounded, equal-sized and crowded. There is a long,
narrow apical slit on the convex side. Rare from 35 to 100 fathoms.