WEST AMERICAK PYEAMIDELLID MOLLUSKS. 165 



spiral keels, which grow successively weaker from the periphery to 

 the umbihcal region, the last three being very fine. Spaces sepa- 

 rating the cords equal to them, crossed b}^ numerous slender, axial 

 threads. Aperture irregularly ovate, posterior angle obtuse; outer 

 Up strong, rendered decidedly sinuous by the axial ribs; columella 

 short, decidedly twisted, strongly curved, reflected, reenforced by 

 the base and provided with a deep-seated fold at its insertion; parietal 

 wall glazed with a thin callus. 



The type (Cat. no. 206900, U.S.N.AI.) comes from Terminal Island, 

 California. It has six post-nuclear whorls and measures: Length 

 5 mm., diameter 2.3 mm. 



ODOSTOMIA (CHRYSALLIDA) VINCTA, new species. 

 Plate 17, fig. 4. 



Shell elongate-ovate, white. Nuclear whorls deeply obliquely 

 immersed in the first of the succeeding turns. Post-nuclear whorls 

 flattened, strongly contracted at the periphery, well shouldered 

 at the summit, marked by strong, somewhat retractive axial ribs, 

 wliich terminate at the posterior edge of the firs.t supraperipheral 

 keel, wliich is smooth. Of these ribs, 18 occur upon the second, 20 

 upon the third, 22 upon the fourth, and 27 upon the penultimate 

 turn. In addition to the axial ribs the whorls are marked by four 

 spiral keels, which equal the ribs in strength and render their junction 

 nodulous. The spaces inclosed by the axial ribs and spiral cords 

 are well impressed round pits. Sutures strongly channeled. Periph- 

 ery of the last whorl marked by a strong groove. Base of the 

 last whorl well rounded, marked by five spiral cords, which grow 

 successively a little weaker from the periphery to the umbilical area. 

 The spaces between these cords are marked by slender spiral threads, 

 wdiich correspond to the ribs. on the spire. Aperture oval, posterior 

 angle obtuse; outer lip thin, rendered wavy by the spiral cords; 

 columella moderately strong, decidedly curved, reflected, and 

 reenforced by the base, provided with a slender fold at its insertion. 



The type (Cat. no. 162762, U.S.N.AI.) comes from San Pedro, 

 Cahfomia. It has six post-nuclear whorls and measures: Length 

 2.7 mm., diameter 1.3 mm. Another specimen was identified for 

 Mr. Berry from the same locality. 



ODOSTOMIA (CHRYSALLIDA) FASCIATA Carpenter. 



Plate 17, fig. 2. 



Chrysallida fasciata Carpenter, Cat. Mazatlan Shells, 1856, p. 423. 



Shell elongate-ovate, white. Nuclear whorls small, obliquely im- 

 mersed in the first of the succeeding tm^ns. Post nuclear whorls 

 moderately rounded, ornamented by decidedly retractive axial ribs 

 2565— Bull. 68—09 12 



