364 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.40. 



the spaces which separate them. In addition to the spiral cords, the 

 whorls are marked by rather poorly developed, rounded, axial ribs, 

 of 'which 14 occur upon the first, 16 upon the second, 18 upon the 

 third and fourth, 20 upon the fifth and sixth, 22 upon the seventh and 

 eighth, and 24 upon the penultimate turn. The intersections of the 

 spiral cords and axial ribs form rather rounded cusps which slope 

 more gently anteriorly than posteriorly, while the spaces inclosed 

 between them are rather shallow, quadrangular pits having their long 

 axes parallel with the spiral sculpture. Sutures moderately con- 

 stricted, showing the posterior edge of the first basal cord. In addi- 

 tion to the above sculpture, the entire surface of the spire is marked 

 by very slender lines of growth and, on the last whorl, by very 

 slender, intercalated, spiral lirations between the cords. Periphery 

 of the last whorl marked by a channel equal to the space between the 

 cords on the spire. Base moderately long, well rounded, ornamented 

 with six, strong, spiral keels which decrease regularly in size and 

 spacing from the periphery to the columella. Aperture irregularly 

 oval, strongly channeled anteriorly; posterior angle acute; outer lip 

 thin, showing the external sculpture within, rendered decidedly wavy 

 at the edge by the external sculpture; columella moderately long, 

 somewhat twisted, and reflected; parietal wall covered with a thick 

 callus. 



The type (Cat. No. 32213, U.S.N.M.) comes from Monterey, 

 California. It has lost the nucleus and probably the first post- 

 nuclear turn; the ten remaining turns measure: Length 12.5 mm., 

 diameter 4:2 mm. 



CERITHIOPSIS TUMIDA Bartsch. 



Plate 41, fig. 3. 



Bittium tumidum, Bartsch, Proc. U. S. Nat. Mus., vol. 33, 1907, pp. 179-180. 



Shell medium size, light yellowish-brown, shining. Nuclear 

 whorls decollated. Post-nuclear whorls somewhat inflated, well 

 rounded, separated by a constricted suture and ornamented with 

 strong tuberculate axial ribs, of which there are 18 upon the second of 

 the remaining whorls and 22 upon the penultimate turn. In addition 

 to the axial ribs there are four, unequally broad, low, spiral ridges 

 between the sutures, which are much wider than the spaces which 

 separate them, the latter appearing as strongly incised lines. The 

 intersection of these ridges and the ribs form the tubercles. The 

 whorls slope gently from the second spiral ridge toward the summit 

 and the first row of tubercles, which is only feebly developed and is 

 located on the sloping shoulder. The second set of tubercles are 

 rounded, while the third and fourth rows are decidedly elongated. 

 Periphery of the last turn marked by a strong smooth spiral keel, 

 which is separated from the supraperipheral keel by a mere constric- 

 tion. Base rather short, without keel, marked only by lines of growth. 



