164 BULLETIN 68, UNITED STATES NATIONAL MUSEUM. 



specimen and a very young shell. The large one has six post-nuclear 

 whorls and measures: Length 4.8 mm., diameter 1.7 mm. 



ODOSTOMIA (CHRYSALLIDA) PROMECES, new species. 



Plate 18, figs. 2, 2a. 



Shell elongate-ovate, vitreous. Nuclear whorls deeply obliquely 

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

 tilted edge of the last volution projects, which is marked by five 

 slender spiral threads. Post-nuclear whorls well rounded, strongly 

 contracted at the periphery and slightly shouldered at the summit, 

 marked on all but the first whorl, which is but feebly sculptured, by 

 strong, rounded, decidedly retractive axial ribs, of which 14 occur 

 upon the second, 16 upon the third, and 20 upon the penultimate 

 turn. In addition to the ribs, the whorls are marked between the 

 sutures, by four low, broad, spiral bands, separated by narrow channels 

 which render their junction with, the ribs decidedly nodulous. On 

 the last two whorls the peripheral cord is apparent in the strongly 

 constricted suture. Periphery of the last whorl marked by a strong 

 cord. Base well rounded, marked by three subequal spiral cords and a 

 plain area about the umbihcus. The grooves separating these cords 

 are marked by many slender axial threads. Aperture ovate, posterior 

 angle obtuse; outer lip thin, showing the external sculpture within; 

 columella moderately strong, slightly reflected, reenforced by the 

 base, provided with a fold at its insertion. 



The type (Cat. no. 162777, U.S.N.M.) comes from Todos Santos 

 Bay, Lower California. It has five post-nuclear whorls and measures : 

 Length 2.5 mm., diameter 1.1 mm. 



ODOSTOMIA (CHRYSALLIDA) PULCHERRIMA, new species. 

 Plate 17, fig. 7. 



Shell large, elongate-oval, vitreous. Nuclear whorls small, smooth, 

 deeply obhquely immersed in the first post-nuclear turn, above w4iich 

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

 strongly rounded, decidedly contracted at the sutures and strongly 

 shouldered at the summit. The first is marked by four slender spiral 

 cords and numerous exceedingly fine axial threads. The next three 

 have twenty strong, rounded, axial ribs, which terminate at the 

 posterior edge of the fourth keel, leaving this smooth. On the last 

 whorl the ribs are decidedly enfeebled, being replaced by numerous 

 axial threads. The spiral sculpture consists of four strong cords 

 between the sutures, the three which cross the ribs form strong 

 nodules at their junction with them, while the supraperipheral one 

 is smooth. Suture strongly impressed, shghtly channeled. Periph- 

 ery and base of the last whorl well rounded, marked by eight 



