154 BULLETIN 68, UNITED STATES NATIONAL MUSEUM. 



second and third and 20 upon the penultimate turn. In addition to 

 the axial ribs the whorls are marked by four very broad, low spiral 

 cords, which are separated by mere incised lines between the sutures, 

 which render their junction vrith the axial ribs very strongly nodu- 

 lous. Sutures constricted, showing a portion of the peripheral cord. 

 Periphery of the last whorl marked by a strong, well rounded spiral 

 cord. Base of the last whorl decidedly attenuated, marked by 

 seven subequal spiral cords, the spaces between which are marked 

 by numerous slender, axial threads. Aperture elongate-ovate, 

 decidedly effuse anteriorly; posterior angle acute; outer lip thin, 

 showing the external sculpture within, rendered sinuous by the 

 spiral cords; columella long, moderately strong, somewhat sinuous, 

 reflected, reenforced by the base, and provided with a fold at its 

 insertion. 



The type (Cat. no. 206899, U.S.N.M.) comes from San Pedro Bay, 

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

 2.5 mm., diameter 1.2 mm. 



ODOSTOMIA (CHRYSALLIDA) ASTRICTA Dall and Bartsch. 



Plate 16, fig. 2. 



Odostomia (Chrysallida) astricta, Dall and Bartsch, Proc. U. S. Nat. Mus., vol. 

 33, 1907, p. 515, pi. 46, fig. 1. 



Shell elongate-conic, bluish-white. Nuclear whorls decollated. 

 Post-nuclear whorls very slightly rounded, separated by deeply chan- 

 neled sutures. In this species the axial ribs exceed the four spiral 

 keels in strength, their junction forming elongated tubercles the long 

 axis of which coincides with the spiral keels. The axial ribs, of 

 which there are 16 upon all of the turns, slant decidedly backward 

 near the aperture. They are rather distantly spaced and the spaces 

 inclosed between them and the spiral keels are deep oblong pits, 

 the long axis of which coincides with the spiral sculpture. Periphery 

 of the last whorl marked by a deep, wide channel across which the 

 ribs extend feebly to the first subperipheral keel. Base rather long 

 and well rounded, marked by seven rather narrow, slender spiral keels 

 which successively decrease in strength from the periphery to the 

 umbilical area, the anterior ones being only faintly indicated; the 

 spaces which separate the keels are about twice as wide as the keels 

 and are crossed by many very slender raised axial threads. Aper- 

 ture oval, outer lip rather thick, columella twisted, reenforced by the 

 attenuated base and provided with a moderately strong fold at its 

 insertion; parietal wall covered by a strong callus. 



The type (Cat. no. 196280, U.S.N.M.) was collected by Mr. F. L. 

 Button at Monterey, Cahfornia; it has the six last whorls remaining, 

 having lost the nucleus and probably the first post-nuclear turn, and 

 measures: Length 2.9 mm., diameter 1.2 mm. 



