WEST AMERICAN PYRAMIDELLID MOLLUSKS. 171 



nuclear whorls slightly rounded, strongly tabulatedly shouldered at 

 the summit, and decidedly sulcate at the periphery, marked by 

 strong, well-rounded, curved, somewhat retractive axial ribs, of 

 which 22 occur upon the second, 26 upon the third, and 30 upon the 

 penultimate turn; on the first they are obsolete. Intercostal spaces 

 well impressed, about as wide as the ribs. The posterior edge of 

 the peripheral sulcus coincides with the summits of the whorls, 

 which render the sutures profoundly channeled. The sulcus is bor- 

 dered on each side by a well-rounded, slender, spiral cord, which 

 forms low tubercles at the junction with the ribs. The peripheral 

 sulcus is crossed by the undiminished axial ribs, which break it up 

 into a series of deep pits. Base of the last whorl somewhat attenu- 

 ated, with a shallow pit at the umbilical region, marked by the con- 

 tinuations of the axial ribs, which here have a decidedly retractive 

 slant, and about twelve slender, spiral lirations. Aperture oval; 

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

 within; columella stout, curved, reenforced by the base, provided 

 with a well-developed fold at the insertion of the columella; parietal 

 wall covered by a thin callus. 



The type (Cat. no. 106519, U.S.N.M.) and another specimen come 

 from Point Abreojos, Lower California. The type has five post- 

 nuclear whorls and measures: Length 2.2 mm., diameter 1.1 mm. 



Three additional specimens fi'om the same locality have been 

 examined in Mr. Delos Arnold's collection. 



Named for Professor Ewald Poppe. 



Subgenus HALDKA Dall and Bartsch. 

 Haldra Dall and Bartsch, Proc. Biol. Soc. Wash., vol. 17, 1904, p. 11. 

 Odostomias with more or less irregular, acute axial ribs extending 

 from the summits of the whorls to the umbilical region, crossed by 

 subequally spaced acute spiral ridges between the sutures and on the 

 base. The intersections of the ribs and spiral ridges are thickened, 

 but scarcely nodulous, lending the shell a very rough appearance. 

 Tyjpe. — Ohrysallida jyliotis Carpenter. 



ODOSTOMIA (HALDRA) PHOTIS Carpenter. 



Plate 18, fig. 8. 



Chrysallida photis Carpenter, Cat. Mazatlan Shells, 1856, p. 425; -\-Chrysallida 

 clalhratula Carpenter, Cat. Mazatlan Shells, 1856, p. 424; not Chemnitzia 

 clathratula C. B. Adams. 



Shell small, pupiform, white. Nuclear whorls at least two, form- 

 ing a depressed helicoid spire, whose axis is at right angles to that 

 of the succeeding turns, in the first of which it is about one-half 

 immersed. Post-nuclear whorls well rounded, moderately con- 

 contracted at the suture, slightly shouldered at the summit, marked 

 by strongly raised, narrow, somewhat retractive axial ribs, of which 

 12 occur upon the first, 14 upon the second, and about 20 upon 



