156 BULLETIN 68^ UNITED STATES NATIONAL MUSEUM. 



channels. In addition to these spiral cords the whorls are marked by 

 weak axial ribs which extend only feebly to tlie first supra-peripheral 

 cord, rendering the junction with the cords feebly nodulous. Sutures 

 strongly constricted, not channeled. Periphery of the last whorl 

 marked by a spiral cord. Base well rounded, slightly channeled 

 anteriorly, marked by nine spiral cords which become successively 

 weaker and closer spaced from the periphery to the umbilical area. 

 The spaces between the cords are marked by numerous slender axial 

 tlireads. Aperture oval, efTuse anteriorly; posterior angle acute; 

 outer lip thin, showing the external sculpture within; columella 

 moderately strong, twisted, strongly reflected, reenforced by the 

 base, provided with a strong fold at its insertion. 



The type (Cat. no. 162770, U.S.N.M.) comes from San Hipohto 

 Point, Lower California. It has five post-nuclear whorls and meas- 

 ures: Length 3.5 mm., (hameter L7 mm. 



ODOSTOMIA (CHRYSALLIDA) LAPAZANA. new species. 



Plate 16, figs. 9, 9a. 



Shell broadly ovate, white. Nuclear whorls smooth, deeply 

 obliquely immersed in the first of the succeeding turns, above which 

 only the tilted edge of the last volution projects. Post-nuclear 

 whorls moderately contracted at the sutures, strongly slopingly 

 shouldered at the summit, where the angle of the shoulder falls on the 

 second spiral keel. The whorls are marked by well developed, nodu- 

 lous axial ribs, of which 20 occur upon all the whorls. Intercostal 

 spaces about twice as w4de as the ribs, crossed by five equal spiral 

 cords, wliich are about half as strong as the ribs and render them 

 nodulous at their junction. The first spiral cord is a little posterior 

 to the middle of the shoulder. The spaces inclosed b}^ the ribs and 

 cords are deep, rectangular pits, the long axis of which coincides 

 with the spiral cords. Sutures strongly marked, but not channeled. 

 Periphery of the last whorl marked b}^ a spiral cord to the posterior 

 extremity of which the axial ribs extend, but wdiose summits they do 

 not cross. Base short, well rounded, marked by nine spiral keels 

 which are about as wide as the spaces that separate them, decreasing 

 successively in strength and spacing from the periphery to the 

 umbilical area. The grooves between the spiral cords are marked by 

 numerous fine, axial raised threads. Aperture oval, slightly efi'use 

 anteriorly; posterior angle obtuse; outer lip thin; columella slender, 

 strongly reflected, provided with a fold at its insertion. 



The type (Cat. no. 162778, U.S.N.M.) and two specimens were 

 dredged at U. S. Bureau of Fisheries station 2823, in 26.5 fathoms, 

 off La Paz, Lower California. The type has five post-nuclear whorls 

 and measures: Length 2.8 mm., diameter 2.1 mm. 



