WEST AMERICAN PYRAMIDELLID MOLLUSKS. 155 



ODOSTOMIA rCHRYSALLIDA) COOPERI Dall and Bartsch. 



Plate 16, fig. 4. 



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

 33, 1907, pp. 514, 515, pi. 46, fig. 7. 



Shell broadly conic, white. Nuclear whorls smooth, largely 

 obliquely immersed in the first of the succeeding turns above which 

 only about half of the last turn projects. Post-nuclear whorl mod- 

 erately rounded, slopingly shouldered at the summit, the shoulder 

 bearing the first of the four stronger tuberculate spiral ridges. The 

 connections which join the tubercles in the spiral series are a little 

 more strongly developed than those which link them vertically, the 

 spaces inclosed between them being deep squarish pits. The tuber- 

 cles are very prominent and rounded; there are about 16 upon the 

 second, 20 upon the third, and 26 upon the penultimate turn. The 

 axial series slants retractively from the posterior suture. Sutures 

 deep and broad, considerably wider than the spaces between the keels. 

 Periphery of the last whorl deeply channeled, the channel marked by 

 a 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 colu- 

 mella, being less distinct and considerably broader than the rest. The 

 channels 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. About five of these 

 threads fall in the space between two tubercles on the spire, in the 

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

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

 nal sculpture within; columella somewhat twisted, revolute ante- 

 riorly, 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. 162771, U.S.N.M.) was collected by Doctor Dall 

 at Monterey, California. It has five post-nuclear whorls and meas- 

 ures: Length 3.1 mm., diameter, 1.4 mm. 



ODOSTOMIA (CHRYSALLIDA) HIPOLITENSIS, new species. 

 Plate 16, fig. 8. 



Shell very elongate-ovate, bluish-wliite. Nuclear whorls deeply 

 obhquely impressed in the first of the succeeding turns. Post- 

 nuclear whorls well rounded, marked by four strong spiral cords 

 between the sutures, which are separated by narrow, deeply incised 



