Bulletin - United States National Museum - Smithsonian Institution

168 BULLETIN 91, UNITED STATES NATIONAL MUSEUM.
nuclear whorls, and measures: Altitude, 1.2 mm.; greater diameter,
3 mm.
VITRINELLA FACIRA, new species.
Plate 34, figs. 5, 6, 7.
Shell small, very depressed helicoid, thin, bluish white. The
nucleus consists of two stages: In the first, embracing one and onehalf
turns, the surface is smooth; in the second stage, which embraces
a little more than a turn, the surface is marked by numerous,
closely spaced, slender, spiral lirations. Postnuclear turns one and
one-fourth, appressed at the summit, well rounded, smooth, marked
by exceedingly fine lines of growth only. Periphery of the last whorl
well rounded. Base openly umbilicated, the umbilicus occupying a
little more than one-third of the diameter of the base, showing all
the whorls within, which are well rounded and marked by lines of
growth only. Aperture subcircular.
The type, Cat. No. 249767a, U.S.N.M., comes from Port Alfred
(Coll. No. 1039). It measures: Altitude, 0.8 mm.; greater diameter,
2 mm.
VITRINELLA (DOCOMPHALA) ARIFCA, new species.
Plate 36, figs. 7, 8, 9.
Shell minute, rather thick, semitranslucent, bluish white. Nuclear
whorls one and one-half, well rounded, polished, smooth. Postnuclear
turns one and one-fourth, strongly rounded, marked by two
slender spiral cords at the summit and microscopic spiral striations
on the rest of the surface. In addition to the spiral sculpture
the turns are marked by fine lines of growth. On the outer edge
of the aperture a number of strongly incised spiral scratches make
their appearance. Sutures well impressed. Periphery of the last
whorl well rounded. Base well rounded, strongly umbilicated.
The umbilicus is limited exteriorly by a strong, slightly tuberculated,
spiral cord. Three additional, strongly tuberculated, spiral cords,
which decrease in strength from the outer edge inward, mark the
inner wall of the umbilicus. The posterior portion of the base,
between the limiting spiral cord of the umbilicus and the periphery,
is smooth, while the other half adjoining the spiral cord is marked
by decidedly retractively slanting, oblique, slender, axial ribs which
anastomose with the spiral cord limiting the umbilicus. Aperture
circular; outer lip very thick; inner lip very strong and reflected,
strongly curved within, the outer edge oblique and straight. The
posterior angle of the aperture is filled by a strong callus.
The type and another specimen of this species, Cat. No. 250554,
U.S.N.M., come from Port Alfred (Coll. No. 1427). The type measures:
Altitude, 0.6 mm.; greater diameter, 1.1 mm.