no. 1823. MOLLUSKS OF THE GENUS CERITHIOrSIS—BARTSCH. 351 



Post-nuclear whorls moderately rounded, appressed at the summit, 

 ornamented with three spiral cords, of which the first is at the summit, 

 which on the first five whorls is scarcely apparent; beginning with 

 the sixth turn, it increases in size until on the last volution it almost 

 equals the other two. The third cord is about as far posterior to the 

 suture as it is from the second cord, which is halfway between the 

 first and third. The spiral cords are not quite as wide as the spaces 

 that separate them. In addition to the spiral cords, the whorls are 

 marked by low, almost vertical, axial ribs, which are less strong than 

 the spiral cords and render their intersections with these cuspidate. 

 Of the axial ribs, 16 occur upon the second to fourth, 18 upon the 

 fifth and sixth, 20 upon the seventh, 22 upon the eighth, and 24 upon 

 the ninth and penultimate turn. The tubercles formed by the junction 

 of the first cord and the axial ribs are well rounded ; those formed by 

 the junction of the median cord and the ribs are truncated anteriorly 

 and posteriorly, sloping a little more gently anteriorly than pos- 

 teriorly; those formed by the junction of the third cord and the ribs 

 are decidedly truncated posteriorly, sloping gently anteriorly. The 

 spaces inclosed between the axial ribs and the spiral cords are strongly 

 impressed, squarish pits. Suture well marked, showing the posterior 

 edge of the peripheral cord. Periphery of the last whorl marked by 

 a strong cord, separated from the supraperipheral cord by a sulcus 

 almost as wide as that which separates the supraperipheral cord from 

 the median and, like it, crossed by the continuations of the axial ribs 

 which terminate at the posterior border of the peripheral cord. Base 

 rather short, concave, marked by two, strong, spiral cords and a 

 slender fasciole, the latter surrounding the columella at its insertion, 

 while the former divides the space between it and the peripheral cord 

 into equal areas. In addition to the above sculpture, the entire base 

 and spire are marked by numerous slender, incremental lines. Aper- 

 ture irregularly subquadrate, strongly channeled anteriorly; posterior 

 angle obtuse; outer lip thin, rendered sinuous at the edge by the 

 external sculpture, which is apparent in the aperture; columella 

 short, stout, twisted, with the free edge reflected; parietal wall glazed 

 with a thin callus. 



The type has ten post-nuclear whorls and measures: Length 7.2 

 mm., diameter 1.2 mm. It and twenty-one additional specimens 

 (Cat. No. 195198, U.S.N.M.) come from Whites Point, San Pedro, 

 California. Cat. No. 195199, U.S.N.M., contains four specimens, 

 also from San Pedro, Califorma. 



