408 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.40. 



upon all but the penultimate turn, which has 18. The intersections 

 of the axial ribs and spiral cords form elongate tubercles, which have 

 their long axis parallel with the spiral sculpture. The spaces inclosed 

 between the axial ribs and spiral cords are rectangular pits on the 

 early whorls and broad, incised lines on the later ones. Sutures 

 slightly constricted. Periphery of the last whorl angulated, marked 

 by a spiral cord. Base short, slightly concave hi the middle, marked 

 by six spiral cords which grow successively weaker from the periph- 

 ery to the umbilical region. In addition to the above sculpture, the 

 entire surface of spire and base is marked by fine lines of growth and 

 numerous exceedingly fine, spiral striations. Aperture quadrangular, 

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

 the external sculpture within, rendered sinuous at the edge by the 

 external sculpture; columella moderately strong, twisted, and reflected; 

 parietal wall glazed with a thin callus. 



The type and 2 specimens (Cat. No. 195156, U.S.N.M.) were dredged 

 in 4 fathoms at San Pedro, California. The type has ten post- 

 nuclear whorls and measures: Length 10 mm., diameter 3.3 mm. 



BITTIUM OLDROYDvE, new species. 

 Plate 51, fig. 5. 



Shell very large, chestnut brown. (Nuclear whorls decollated in 

 all our specimens.) Post-nuclear whorls moderately rounded, orna- 

 mented with three spiral keels, which are truncated on their posterior 

 margin and slope gently anteriorly until they fuse with the general 

 mass of the shell. These keels divide the space between the sutures 

 into four almost equal parts, the space between the summit and the 

 first keel being a little narrower than the rest. In addition to the 

 spiral keels, the whorls are marked by slightly retractive axial ribs, 

 of which 12 occur upon the second, 14 upon the third and fourth, 10 

 upon the fifth to seventh, 18 upon the eighth, 20 upon the ninth and 

 tenth, and 22 upon the penultimate turn. These ribs extend from 

 the summit to the suture. Their intersections with the spiral cords 

 form strong, cusped nodules, which slope more abruptly anteriorly 

 than posteriorly. The spaces inclosed between the spiral keels and 

 the axial ribs are considerably wider than the ribs or cords and form 

 squarish pits. Sutures strongly marked, showing a slender, smooth, 

 peripheral cord (to which the axial ribs extend) on almost all the 

 turns. Periphery and base of the last whorl well rounded, marked 

 by six well-rounded spiral cords, which grow successively weaker, 

 and a little more closely spaced from the periphery to the umbilicus. 

 Entire surface of spire and base crossed by numerous slender axial 

 lines of growth. Aperture moderately large, channeled anteriorly; 

 posterior angle obtuse; outer lip rendered sinuous by the external 



