N0.1574. WEST AMERICAN PYRAMIDELLID.E— BALL AND BARTSCH. 515 



weak extension of the axial bars which terminate at the first supra- 

 peripheral keel. Base prolonged, well-rounded, marked by seven 

 strong- moderately raised, spiral keels which, like the channels that 

 separate them, diminish regularly in width from the periphery to the 

 umbilical area; the last, the eighth, immediately behind the columella, 

 being less distinct and considerably broader than the rest. The chan- 

 nels between the keels are about equal to the keels in width and are 

 crossed by numerous very slender raised threads, which extend up on 

 the sides of the keels but do not cross them. Al)Out five of these 

 threads fall in the space between two tul>ercles on the spire, in the 

 first supra-peripheral groove. Aperture oval, large, efluse anteriorly, 

 posterior angle obtuse, outer lip rather thick, not showing the exter- 

 nal sculpture within; columella somewhat twisted, re volute anteriorly, 

 reenforced by the attenuated base, and provided with a weak fold at 

 its insertion; parietal wall covered by a callus which joins the columella 

 with the posterior angle of the aperture and renders the peristome 

 almost complete. 



' The type (Cat. No. 162TT1. T.S.N.M.) was collected ])y Doctor Dall 

 at Monterey, California. It has five postnuclear whorls and measures: 

 Length, 3.1 mm.; diameter, l.-t nmi. 



ODOSTOMIA (CHRYSALLIDA) ASTRICTA, new species. 

 Plate XJ.VI, %. 1. 



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

 nuclear whorls very slightly rounded, separated by deeply chan- 

 nelled sutures. In this species the vertical ribs exceed the four spiral 

 keels in strength, their junction forming elongated tubercles the long 

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

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

 toward 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 feebl}^ 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 vertical 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 Monterev, California; it has the 6 last whorls remaining, 

 having lost the nucleus and probabl}' the first post-nuclear turn, and 

 measures: Length, 2.9 mm.; diameter, 1.2 mm. 



