400 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.40. 



what wavy at the edge; columella very oblique, slightly twisted, 

 and reflected; parietal wall glazed with a thin callus. 



The type (Cat. No. 195163, U.S.N. M.) is a young specimen having 

 six post-nuclear whorls and measures: Length 6.1 mm., diameter 2.8 

 mm. It comes from the Gulf of California. 



BITTIUM (SEMIBITTIUM) NITENS Carpenter. 



Plate 57, fig. 2. 



Bittium nitens Carpenter, Rep. Brit. Ass. Adv. Sci. for 1863, 1864, p. 618. 

 Bittium nitens Carpenter, Ann. Mag. Nat. Hist., ser. 3, vol. 13, 1864, p. 479. 



Shell elongate-conic, white, semitranslucent, variegated with rust 

 brown, shiny. Nuclear whorls a little more than one, smooth. 

 Early post-nuclear whorls with a decidedly sloping shoulder which 

 extends from the middle of the whorl to the appressed summit; the 

 later ones well rounded. The early whorls are ornamented with 

 three spiral cords, of which one is at the summit, the second at the 

 angle of the shoulder, and the third a little posterior to the suture. 

 On the third post-nuclear whorl a fourth cord makes its appearance at 

 the summit, increasing rapidly in size until it equals the other three. 

 In addition to the spiral sculpture, the whorls are marked by some- 

 what irregular, variously sloping, moderately rounded, axial ribs, 

 of which 12 occur upon the second, 10 upon the third and fourth, 

 12 upon the fifth, 14 upon the sixth and the penultimate turn. The 

 junctions of the axial ribs and the spiral cords form well-rounded 

 tubercles, which slope more abruptly posteriorly than anteriorly, 

 while the spaces inclosed between them are rectangular pits, having 

 their long axes parallel with the spiral sculpture. Sutures some- 

 what constricted. Periphery of the last whorl marked by a slender 

 sulcus. Base short, rounded, marked by three equal spiral cords, of 

 which two occur immediately below the periphery, while the third 

 encircles the base of the columella. Entire surface of spire and 

 base crossed by numerous lines of growth. Aperture subquadrate, 

 channeled anteriorly; posterior angle obtuse; outer lip thin, showing 

 the external sculpture within, rendered sinuous by the external sculp- 

 ture; columella oblique, slender, and somewhat revolute; parietal wall 

 glazed with a thin callus. 



The type (Cat. No. 4068, U.S.N.M.) comes from Cape San Lucas, 

 Lower California. It has eight post-nuclear whorls, and measures: 

 Length 5.7 mm., diameter 0.2 mm. 



