Bulletin - United States National Museum - Smithsonian Institution

SOUTH AFRICAN MARINE MOLLUSKS. 133
numerous, decidedly retractive, incremental lines and exceedingly fine
spiral striations. Sutures moderately impressed; periphery of the
last whorl inflated, well rounded; base short, narrowly umbilicated,
well rounded. Aperture subcircular; posterior angle obtuse; outer lip
thin; inner lip strongly curved and partly reflected over the umbilicus,
continuing as a thin callus over the parietal wall.
The type and seven specimens, Cat. No. 187072, U.S.N.M., came
from Port Alfred (Coll. No. 610). The type has a little more than
five whorls, and measures: Length, 2.1 mm.; diameter, 1.1 mm. Cat.
No. 227745, U.S.N.M., contains three specimens from the same locality
(Coll. No. 840). Another specimen, Cat. No. 250428, U.S.N.M., also
comes from Port Alfred (Coll. No. 1301).
MICROSETIA HELGA, new species.
Plate 6, fig. 3.
Shell small, elongate-conic, yellowish white. Nuclear whorls not
differentiated from the succeeding turns ; all the whorls well rounded,
appressed at the summit, through which the preceding whorl shines,
which lends the shell the aspect of having a double suture. Sutures
moderately impressed. Periphery of the last whorl somewhat in-
flated, well rounded. Base moderately long, narrowly umbilicated,
well rounded; entire surface of spire and base marked by exceedingly
fine incremental lines only. Aperture oval; posterior angle obtuse;
outer lip thick; inner lip strongly curved and quite thick, reflected
over the umbilicus; parietal wall covered with a thick callus.
The type and another specimen, Cat. No. 187056, U.S.N.M., came
from Port Alfred (Coll. No. 594). The type has six whorls and measures:
Length, 2.7 mm.; diameter, 1.5 mm. Cat. No. 250423, U.S.N.M.,
contains another specimen from Port Alfred (Coll. No. 1296).
MICROSETIA IRMA, new species.
Plate 21, fig. 9.
Shell elongate-ovate, very thin, transparent. Nuclear whorls not
differentiated from the postnuclear turns. Postnuclear whorls well
rounded, appressed at the summit, marked by exceedingly fine, re-
tractive lines of growth and closely spaced, microscopic spiral striations.
Sutures moderately constricted. Periphery of the last whorl
strongly rounded. Base moderately long, strongly rounded, very
narrowly umbilicated. Aperture ovate; posterior angle acute; outer
lip very thin; inner lip very thin, evenly curved and slightly reflected;
parietal wall glazed with a thin callus.
The type and another specimen, Cat. No. 249724, U.S.N.M., come
from Port Alfred (Coll. No. 996). The type has four whorls, and
measures: Length, 1.6 mm.; diameter, .1 mm.
80737°— Bull. 91—15 10