404 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 40. 



cusps which are suddenly truncated posteriorly and slope gently 

 anteriorly, the spaces inclosed between them being small, rounded 

 pits. Sutures channeled. Periphery of the last whorl marked by a 

 slender cord. Base moderately prolonged, ornamented by six spiral 

 cords, of which the two immediately anterior to the periphery and 

 the two at the base of the columella are decidedly stronger than the 

 rest. Aperture rather large, channeled anteriorly; posterior angle 

 acute ; outer lip rendered sinuous by the external sculpture ; columella 

 stout, twisted, somewhat revolute, and reflected; parietal wall glazed 

 with a moderately thick callus. 



The type (Cat. No. 194413, U.S.N.M.) comes from Deadmans 

 Island, San Pedro, California. It has lost the nucleus and probably 

 the first two post-nuclear turns; the nine remaining measure: Length 

 12.1 mm., diameter 4 mm. A young specimen from the same lot, 

 which furnished the description of the nucleus, has ten post-nuclear 

 whorls, and measures: Length 9.2 mm., diameter 3.3 mm. 



Specimens examined. 



1 Type. 

 BITTIUM (LIROBITTIUM) MUNITUM Carpenter. 



Plate 53, figs. 1 and 2. 



Cerithiopsis munita Carpenter, Rep. Brit. Ass. Adv. Sci. for 1863, 1864, p. 628 



and p. 660. 

 Cerithiopsis munita Carpenter, Ann. Mag. Nat. Hist., ser. 3, vol. 15, 1865, p. 31. 



Shell elongate-conic, yellowish white. Nuclear whorls a little more 

 than one (with the sculpture abraded in all our specimens). Post- 

 nuclear whorls strongly shouldered at the summit, marked by three 

 strong, equal and equally spaced spiral keels, which are a little wider 

 than the spaces that separate them. In addition to the spiral keels, 

 the whorls are marked by somewhat retractive axial ribs, of which 18 

 occur upon the second, 20 upon the third, 24 upon the fourth and 

 fifth, and 28 upon the penultimate. The intersections of the axial 

 ribs and spiral keels form strong tubercles, while the spaces between 

 them are well impressed, rounded pits. Sutures subchanneled. 

 Periphery of the last whorl marked by a strong channel, across which 

 the feeble continuations of the axial ribs extend. Base moderately 

 long, marked by six strong spiral cords which grow successively 

 weaker from the periphery to the umbilical area. In addition to the 



