20 BULLETIN 68, UNITED STATES NATIONAL MUSEUM. 



KEY TO THE SPECIES OP THE SUBGENUS VOLUSPA. 



Adult of 11 whorls, slender, length under 15 mm auricoma. 



Adult of 11 whorls, stout, length over 25 mm cerrosana. 



PYRAMIDELLA (VOLUSPA) AURICOMA DaU. 

 Plate 1, fig. 3. 

 Pyramidella auricoma Dall, Blake Report, Gastropoda, 1889, p. 332. 



Shell regularly elongate-conic, yellowish- white, with fine golden 

 yellow spiral lines between the sutures and on the base. Nuclear 

 whorls small, deeply obliquely immersed in the first post-nuclear 

 turn. Post-nuclear turns well rounded, feebly shouldered at the 

 summit, scarcely at all contracted at the sutures. Sutures weakly 

 impressed. Periphery and base of the last whorl well rounded, 

 smooth. Aperture irregularly oval; outer lip thin, reenforced deeply 

 within by five strong spiral cords, one of which is at the periphery, 

 two divide the space between this and the summit into three equal 

 parts, and two a little less strong are on the base; columella strong, 

 straight, posterior fold very strong and lamellar, oblique; anterior 

 two about one-fourth as high as the posterior, very oblique; parietal 

 wall glazed by a thin callus. 



The type (Cat. no. 32268, U.S.N.M) and two additional specimens 

 were collected by Dr. Edward Palmer in the Gulf of California. 

 The type has ten post-nuclear whorls and measures: Length 10.6 

 mm., diameter 3.8 mm. Another specimen (Cat. no. 168681, 

 U.S.N.M.) comes from Mazatlan, Mexico. 



PYRAMIDELLA (VOLUSPA) CERROSANA, new species. 

 Plate 1, fig. 1. 



Shell very large, broadly conic. (Nuclear whorls decollated.) 

 Post-nuclear whorls flattened in the middle, moderately shouldered 

 at the summit, and moderately contracted at the sutures. Sutures 

 well impressed. Periphery and base of the last whorl well rounded. 

 Aperture ?; outer lip reenforced within by seven spiral lirations, 

 one of which is at the periphery, three between this and the suture, 

 of which the one next to the periphery is the strongest of all seven, 

 while the two posterior to it are the weakest; the three anterior to 

 the periphery are equally spaced and grow successively weaker; 

 columella strong, straight; posterior fold very strong, lamellar; 

 anterior two about one-fourth as strong, very oblique. 



The type (Cat. no. 6332, U.S.N.M.) comes from Cerros Island; Lower 

 California. It has lost the nucleus and early whorls; the ten remaining 

 measure: Length 25.5 mm., diameter 10.2 mm. 



