SOUTH AFRICAN MARINE MOLLUSKS. 199 



BORNIA ARFICA, new species. 

 Plate 41, fig. 7; plate 51, fig. 4. 



Shell broadly oval. Umbones decidedly anterior to the middle. 

 Outer surface of the shell marked by numerous very closely spaced, 

 fine, concentric threads, which are a little broader than the spaces 

 that separate them, and numerous, very fine, microscopic, radiating 

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



The type, Cat. No. 2498946, U.S.N.M., comes from Port Alfred 

 (Coll. No. 11 666). It consists of a right valve, and measures: Alti- 

 tude, 2.3 mm.; length, 2.8 mm. 



BORNIA (PYTHINA) ROTUNDATA Deshayes. 

 Plate 51, figs. 5, 6. 



Cat. No. 186969, U.S.N.M., contains two and one-half specimens 

 of this species from Port Alfred (Coll. No. 342). 



BORNIA (PYTHINA) AFRICANA, new species. 

 Plate 42, figs. 1, 2; plate 51, fig. 3. 



Shell rather large, oval, slightly emarginate at the base, with the 

 umbones decidedly posterior to the middle. The outer surface is 

 marked by fine lines of growth and minute tubercles, which lend it a 

 shagreened appearance. On the anterior end the shell has a few, ill- 

 defined, raised, radiating threads. 



The type and another valve, Cat. No. 187190, U.S.N.M., come from 

 Port Alfred (Coll. No. 741). The type measures: Altitude, 9.5 mm.; 

 length, 13.8 mm. 



Three additional lots are in the collection of the United States 

 National Museum, all from Port Alfred, as follows: Cat. No. 251011, 

 a young specimen (Coll. No. 1528); Cat. No. 251038, one valve (Coll. 

 No. 1555); Cat. No. 251056, one young valve (Coll. No. 1573). 



Genus ROCHEFORTIA Velain. 

 ROCHEFORTIA CONVEXA Gould. 



Plate 45, figs. 1,2; plate 47, fig. 4, young; plate 51, figs. 7, 8, hinge. 

 Kellia conveza Gould, Proc. Bost. Soc. Nat. Hist., vol. 8, p. 34, 1861. 



Shell of suboval outline, wax yellow. Umbones almost median, 

 with the dorsal margin slanting almost equally, anteriorly and pos- 

 teriorly. Both ends equally rounded, and the basal margin gently 

 curved. Entire surface marked by rather irregular, fine lines of 

 growth. Hinge as shown in Plate 51, figs. 7, 8. 



Gould's cotypes, Cat. No. 24244, U.S.N.M., two specimens, were 

 collected by William Stimpson on the North Pacific Exploring Expe- 



