150 BULLETIN 68, UNITED STATES NATIONAL MUSEUM. 



ODOSTOMIA (CHRYSALLIDA) OONISCA, new name. 



Plate 15, fig. 3. 



ChrysalUda ovulum Carpenter, Cat. Maz. Shells, 1856, pp. 423, 424; not Pasithea 

 (=Odostomia) ovulum Lea, 1845. 



Shell ovate, white. Nuclear whorls deeply obliquely immersed in 

 the first post-nuclear whorl above which only the tilted edo;e of the 

 last volution projects. Post-nuclear whorls moderately rounded, 

 strongly contracted at the sutures, moderately shouldered at the 

 summit, marked by the moderately strong, tuberculate, slightly 

 retractive axial ribs, of which 16 occur upon the second and 18 upon 

 the third and penultimate turn. In addition to the axial ribs the 

 whorls are marked by four spiral cords between the sutures which 

 are a little less strong than the axial ribs and render them nodulous 

 at their junction. The spaces inclosed by the ribs and spiral cords 

 are deep round pits. Sutures channeled. Periphery of the last 

 whorl marked by a groove. Base well rounded, marked by six 

 strong, spiral cords which decrease successively in size and spacing 

 from the periphery to the umbilicus. Grooves between the spiral 

 cords marked b}" slender threads corresponding to the axial ribs. 

 Aperture irregularly pyriform, posterior angle acute; outer lip 

 pinched in posteriorly, thin, showing the external sculpture within; 

 columella slender, slightly reflected, provided with a fold at its inser- 

 tion; parietal wall covered with a thin callus. 



Tablet 1982, Liverpool collection, British Museum, contains nine 

 specimens taken from Spondylus and Cliama at Mazatlan, Mexico. 

 A specimen of four whorls measures: Length 1.4 mm., diameter 

 0.7 mm. 



ODOSTOMIA (CHRYSALLIDA) OLDROYDI, new species. 

 Plate 15, figs. 1, la. 



Shell elongate-ovate, vitreous. Nuclear whorls small, obliquely 

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

 the tilted edge which is marked with five raised spiral lirations. Post- 

 nuclear whorls somewhat inflated, well rounded, moderately con- 

 tracted at the sutures, strongly slopingly shouldered at the summit, 

 ornamented with somewhat retractive axial ribs, of wliich 14 occur 

 upon the first, 16 upon the second, 18 upon the third, and 20 upon 

 the penultimate turn. In addition to the axial ribs, the whorls are 

 marked by four spiral cords between the sutures which are as strong 

 as the ribs and render them strongly nodulous at their junction. 

 The second of these ribs below the summit marks the angle of the 

 shoulder. The spaces inclosed by the ribs and cords are strongly 

 impressed oblong pits, the long axis of which coincides with the spiral 

 sculpture. Sutures strongly constricted. Periphery of the last whorl 



