200 BULLETIN 91, UNITED STATES NATIONAL MUSEUM. 



dition in 12 fathoms at the Cape of Good Hope. The larger of these, 

 plate 45, figs. 1, 2, measures: Length, 4.2 mm.; altitude, 3 mm.; diame- 

 ter, 2 mm. 



ROCHEFORTIA SIMILIS Smith. 

 Plate 51, figs. 9, 10. 



There are three lots of this species in the collection of the United 

 States National Museum, all from Port Alfred, as follows: Cat. No. 

 186967, one and one-half specimens (Coll. No. 339) ; Cat. No. 249886, 

 two specimens (Coll. No. 1158); Cat, No. 251052, two valves (Coll. 

 No. 1569). 



ROCHEFORTIA NATALENSIS Smith. 

 Plate 52, figs. 1, 2. 



There are three lots of this species in the collection of the United 

 States National Museum, all from Port Alfred, as follows: Cat. No. 

 186185, one valve (Coll. No. 736); Cat, No. 249890, two specimens 

 (Coll. No. 1162); Cat. No. 249891, two specimens (Coll. No. 1163). 



ROCHEFORTIA ENORA, new species. 

 Plate 45, fig. 5; plate 52, figs. 3, 4. 



Shell oval, rather thick, with the umbones almost median. The 

 surface marked by somewhat irregular, slender, closely spaced lines 

 of growth, and weak, very fine, radiating striations. The character 

 of the hinge is shown in the detailed sketch. 



The type, Cat. No. 251040, U.S.N.M., comes from Port Alfred 

 (Coll. No. 1557). It measures: Altitude, 3 mm.; length, 3.8 mm. 



ROCHEFORTIA ELSA, new species. 



Plate 41, fig. 3; plate 52, figs. 5, 6. 



Shell broadly oval, minute, very thin, semitranslucent, the umbones 

 being situated at the anterior end. Outer surface marked by numer- 

 ous, very fine, concentric lines of growth, which appear as very slender 

 threads. No radiating sculpture is apparent. The character of the 

 hinge is shown in our detailed sketch. 



The type, Cat. No. 251045, U.S.N.M., comes from Port Alfred (Coll. 

 No. 1562). It measures: Altitude, 1.4 mm.; length, 1.8 mm. 



ROCHEFORTIA MILDA, new species. 

 Plate 47, fig. 6; plate 52, figs. 9, 10. 



Shell small, broadly oval, covered by an exceedingly thin perios- 

 tracum, which lends it an iridescent appearance. Umbones slightly 

 anterior to the middle. The posterior margin slightly truncated ; the 

 anterior well rounded. Surface marked by numerous very closely 

 spaced, slender, concentric threads, which are a little wider than the 

 spaces that separate them, and numerous very fine radiating, axial 



