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, semi translucent. 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 meas- 

 ures: Altitude, 1.5 mm.; length, 1.9 mm. 



