102 NAUTILUS Vol. 75 (3)
NEW SPECIES OF HELICODISCUS
FROM THE EASTERN UNITED STATES
By LESLIE HUBRICHT
HELICODISCUS MULTiDENS, new species. Plate 7, D-F; Text fig. 1
Shell discoidal, spire flat or nearly so; whorls 4i/2 to 5; pale
greenish-yellow, dull, opaque. Umbilicus wide and shallow, show-
ing all the whorls, occupying from 45 to 50% of the diameter of
the shell. Whorls well roundfed, slowly increasing, the last slowly
descending; sculptured with numeious, fine, spiral threads. Aper-
ture lunate, the peristome somewhat thickened within. Within
the last quarter whorl there are 3 pairs of teeth on the outer and
basal walls. These teeth are radially elongate, raised on a heavy
callous ridge, and separated by a rounded sinus. Alternating with
these are 3 teeth on the parietal wall. These teeth extend out to
about the center of the whorl, are about twice as broad as high,
the ends are turned forward, the upper end more so than the
lower. Of the 3 sets of teeth the center set is usually more fully
developed than the others. As the shell grows, the teeth farthest
within are absorbed and a new set added near the aperture.
Height, 1.88 mm. Diameter, 4.75 mm. Umbilicus diameter, 2.22
mm. Aperture height, 1.55 mm. 4.5 whorls. Holotype.
Distribution:
BioStor
