Bulletin - United States National Museum - Smithsonian Institution

206 BULLETIN 91, UNITED STATES NATIONAL MUSEUM.
Genus METIS H. and A. Adams.
METIS ORBICULARIS Sowerby.
Cat, No. 187170, U.S.N.M., one valve from Port Alfred (Coll. No.
717).
Genus MACOMA Leach.
MACOMA LITTORALIS Krauss.
Cat. No. 186954, U.S.N.M., three and one-half specimens from
Port Alfred (Coll. No. 324).
MACOMA AFRICANA Sowerby.
Cat, No. 186955, U.S.N.M., two specimens from Port Alfred (Coll.
No. 325). Cat. No. 249862, U.S.N.M., contains two additional
specimens from the same locality (Coll. No. 1134).
Family SEMELIDAE.
Genus SEMELE Schumacher.
SEMELE CAPENSIS Smith.
Cat, No. 249861, U.S.N.M., contains six valves of this species, all
from Port Alfred (Coll. No. 1133).
Genus ABRA (Leach) Lamarck
ABRA AFRICANA, new species.
Plate 45, fig. 7; plate 49, figs. 8, 9.
Shell small, bluish white, covered by a very thin, yellow periostracum.
The umbones fall considerably anterior to the middle, The
anterior dorsal margin slopes more abruptly than the posterior dor-
sal. The ventral is evenly, gently curved. By transmitted light the
valves show microscopic, closely spaced, radiating striations and fine
lines of growth. The hinge is shown in our detailed figure.
The type, Cat. No. 249863, U.S.N.M., comes from Port Alfred
(Coll. No. 1135). It measures: Altitude, 3.7 mm.; length, 5 mm.
Genus THEORA H. and A. Adams.
THEORA ALFREDENSIS, new species.
Plate 45, fig. 8; plate 49, fig. 3.
Shell elongate-oval, polished, thin, semitranslucent. Anterior
dorsal margin sloping much more abruptly than the posterior;
ventral margin evenly rounded. The entire surface of the shell is
marked by exceedingly fine, microscopic, radiating striations, which
are best shown by transmitted light, and coarser lines of growth.
The hinge is shown in our detailed figure.
The type, Cat. No. 251032, U.S.N.M., comes from Port Alfred
(Coll. No. 1549). It measures: Altitude, 5.5 mm.; length, 9.2 mm.