Bulletin - United States National Museum - Smithsonian Institution

SOUTH AFRICAN MARINE MOLLUSKS. 195
PHACOIDES DESPECTA Smith.
Cat. No. 186962, U.S.N.M., one specimen from Port Alfred (Coll.
No. 333).
Family DIPLODONTIDAE.
Genus DIPLODONTA Bronn.
DIPLODONTA AFRICANA, new species.
Plate 47, fig. 5; plate 53, figs. 9, 10.
Shell small, donaciform, thin, semitranslucent. Exterior marked by
numerous, regular and regularly spaced, slender, concentric threads,
which are about as wide as the spaces that separate them. The
incised lines appear as hydrophanous bands. In addition to the
concentric markings, there are irregularly disposed, somewhat dis-
continuous, slender, radiating, hydrophanous lines. The entire
external sculpture is equally visible within. The character of the
hinge is shown in our detailed sketch.
The type, Cat. No. 251029, U.S.N.M., comes from Port Alfred
(Coll. No. 1546). It measures: Altitude, 1.5 mm.; length, 2.2 mm.
Cat. No. 251047, U.S.N.M., contains another specimen from the same
locality (Coll. No. 1564).
DIPLODONTA ALMO, new species.
Plate 47, fig. 1; plate 54, fig. 2.
Shell very thin, semitranslucent, bluish white. Umbones median.
Anterior and posterior dorsal margins sloping evenly. Surface
marked with numerous, equal and equally spaced, slender, concentric
threads which are about half as wide as the spaces that separate them.
In addition to this, there are numerous, very fine, radiating striations.
All the external markings are seen on the inner surface. The charac-
ter of the hinge is shown in our detailed sketch.
The type, Cat. No. 251048, U.S.N.M., comes from Port Alfred
(Coll. No. 1565). It measures: Altitude, 2.8 mm.; length, 3.5 mm.
Genus FELANIELLA Dall.
FELANIELLA ALFREDENSIS, new species.
Plate 48, fig. 5; plate 53, figs. 7, 8.
Shell minute, bluish white, semitransparent, irregularly oval in
outline. Umbones projecting anteriorly. Surface marked by fine
incremental fines and very fine, somewhat divaricating, closely
spaced, radiating striations. The character of the hinge is shown in
our detailed sketch.
The type and another specimen of this species, Cat. No. 251044,
U.S.N.M., come from Port Alfred (Coll. No. 1561). The type measures:
Altitude, 1.5 mm.; length, 1.9 mm.