SOUTH AFRICAN MARINE MOLLUSKS. 201 



threads, which are best pronounced on the posterior portion of the 

 shell. The character of the hinge is shown in our detailed sketch. 



The type and another valve, Cat. No. 249894, U.S.N.M., come from 

 Port Alfred (Coll. No. 1166). The type measures: Altitude, 2.2 mm.; 

 length, 2.5 mm. 



ROCHEFORTIA HELENA, new species. 

 Plate 42, figs. 3, 4; plate 47, fig. 2; plate 52, figs. 7, 8. 



Shell minute, of somewhat irregular cuneate outline, thin, semi- 

 translucent. Umbones a little posterior to the anterior margin. 

 Outer surface marked by exceedingly fine, concentric threads only. 

 The character of the hinge is shown in our detailed sketch. 



The type and another specimen of this species, Cat. No. 187193, 

 U.S.N.M., come from Port Alfred (Coll. No. 744). The type meas- 

 ures: Altitude, 1.2 mm.; length, 1.5 mm. 



Cat. No. 251019, U.S.N.M. contains three additional valves of this 

 species from the same place (Coll. No. 1536). 



ROCHEFORTIA IO, new species. 

 Plate 39, fig. 5; plate 53, figs. 5, 6. 



Shell very minute, of irregular cuneate outline. Prodissoconch 

 marked by fine radiating striations. The succeeding portion, which 

 is separated by a slight constriction from the prodissoconch, is marked 

 by numerous, rather strong, concentric threads, which are about as 

 wide as the spaces that separate them. The character of the hinge 

 is shown in our detailed sketch. 



The type and two other specimens, Cat. No. 251043, U.S.N.M., 

 come from Port Alfred (Coll. No. 1560). The type measures: Alti- 

 tude, 0.9 mm.; length, 1.1 mm. 



ROCHEFORTIA FARMA, new species. 

 Plate 48, fig. 2; plate 53, figs. 1, 2. 



Shell small, oval, covered with a very thin yellowish periostracum, 

 with the umbones about one-third of the entire length of the shell 

 posterior to the anterior margin. Surface marked with rather coarse 

 and somewhat irregular lines of growth, and numerous, fine, radiating 

 striations which are of varying strength and irregular spacing. The 

 character of the hinge is shown in our detailed figure. 



The type and another valve, Cat. No. 249892, U.S.N.M., come from 

 Port Alfred (Coll. No. 1164). The type measures: Altitude, 1.9 mm.; 

 length, 2.5 mm. 



Genus LASEA Leach. 



LASEA TURTONI, new species. 

 Plate 42, figs. 9, 10; plate 53, figs. 3, 4. 



Shell irregularly, broadly oval, white, with the early portion and the 

 hinge suffused with rose purple. The umbones are about opposite the 



