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 periostra- 

 cum. 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. 



