144 BULLETIN 68^ UNITED STATES NATIONAL MUSEUM. 



The type and three specmiens (Cat. no. 106518, U.S.N.M.) come 

 from Scammon Lagoon, Lower California. Tiie type has six post- 

 nuclear whorls and measures: Length 3.4 mm., diameter 1.3 mm. 



ODOSTOMIA (CHRYSALLIDA) EFFUSA Carpenter. 

 Plate 14, figs. 5, 5a. 

 Chrysallida effusa Carpenter, Cat. Mazatlan Shells, 1856, p. 422. 



Shell elongate-conic, vitreous. Nuclear whorls small, smooth, 

 almost completely obliquely immersed in the first of the succeeding 

 turns, above which only the tilted edge of the last volution projects. 

 Post-nuclear whorls flattened, strongly contracted at the sutures and 

 moderately shouldered at the summit, marked by strong, tuberculate 

 retractive axial ribs, of which IS occur upon the first and second and 

 20 upon the remaining turns. In addition to these axial ribs the 

 whorls are marked by four slender, spiral cords between the sutures, 

 which pass over the axial ribs and render them tuberculate at their 

 junction. The spaces inclosed l)y the ribs and cords are rectangular 

 pits, which have their long axis parallel with the spiral cords. Sutures 

 channeled. Periphery of the last whorl marked by a spiral groove. 

 Base of the last whorl well rounded, marked by eight spiral cords 

 which grow successively weaker and closer spaced from the periph- 

 ery to the umbilical area. The w4de grooves between the spiral 

 cords are marked by slender, raised, axial threads, which correspond 

 to the ribs on the spire. Aperture ovate, somewhat effuse anteriorly; 

 posterior angle obtuse, outer lip thin, showing the external mark- 

 ings within; columella stout, strongly reflected, provided with a 

 slender fold at its insertion; parietal wall covered by a strong callus. 



The type, which is on tablet 1980, Liverpool collection, British 

 Museum, came off CJiama at Mazatlan, Mexico. The specimen 

 described and figured (no. 16194, U.S.N.M.) w^as collected by 

 J. Xantus, at Cape St. Lucas, Lower California. It has six post- 

 nuclear whorls and measures: Length 2.8 mm., diameter 1.2 mm. 



ODOSTOMIA (CHRYSALLIDA) PAUPERCULA C. B. Adams. 



Plate 14, fig. 4. 



Cingula {?) paupercula C. B. Adams, Ann. Lye. Nat. Hist, of N. Y., vol. 5, 1852, 

 pp. 405, 406. 



Shell very elongate, conic, bluish-white. Nuclear whorls two, 

 smooth, forming a depressed helicoid spire, whose axis is at right 

 angles to that of the succeeding turns, in the first of which it is about 

 half immersed. Post-nuclear whorls moderately rounded, slightly 

 shouldered at the summit, somewhat contracted at the sutures, 

 marked by four strong spiral cords and axial ribs, which are a little 

 less strong than the cords; 18 of the ribs occur upon the fu'st, 16 

 upon the second to fifth, 20 upon the sixth, and 34 upon the penulti- 



