396 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



vor.. 40. 



the summit, another on the middle of the whorl, while the third is a 

 little above the suture. The succeeding turns show four spiral cords, 

 of which the one at the summit is a little less strong than the rest; 

 the remaining three divide the space between the sutures into foui 

 equal parts. Beginning with the fourth whorl, intercalated cords 

 make their appearance between the primary ones, so that on the last 

 whorl we have an intercalated cord and sometimes two between all 

 the primary cords; these, however, are never quite as strong as the 

 principal ones. In addition to the spiral cords, the whorls are marked 

 by decidedly curved, slender, well-rounded, almost vertical, axial 

 ribs, which are scarcely indicated on the first turn, while 14 of them 

 occur upon the second and third, 16 upon the fourth, 18 upon the 

 fifth and sixth, 22 upon the seventh, 24 upon the eighth, and 26 

 upon the penultimate turn. The intersections of the spiral cords 

 and axial ribs form weakly developed, rounded tubercles which are 

 truncated on their posterior margin, while the spaces enclosed between 

 them are very shallow quadrangular pits. Sutures strongly con- 

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

 by slender, spiral cords of which those immediately below the periph- 

 ery are the strongest and are truncated on the posterior margin, 

 sloping gently anteriorly. Of these cords, seven occur on the base 

 of the type. Aperture rather large, irregularly oval, channeled 

 anteriorly; posterior angle acute; outer lip thin, rendered sinuous by 

 the external sculpture; columella decidedly oblique, strongly curved, 

 and reflected. 



The type (Cat. No. 160076, U.S.N.M.) is one of fifty specimens from 

 Catalina Island, California. It has ten post-nuclear whorls and 

 measures: Length 10.9 mm., diameter 3.8 mm. 



Specwiens examined. 



Type. 



