WEST AMERICAN PYRAMIDELLTD MOLLUSKS. 129 



TURBONILLA (PYRGISCULUS) PAUCILIRATA Carpenter. 

 Plate 12, fig. 10 

 Dunheria pauciUrata Carpenter, Cat. Mazatlan Shells, 1856, p. 434. 



The type and only known individual of this species is an imperfect 

 specimen mounted on tablet 2007 of the Liverpool collection in the 

 British Museum. 



The nucleus is two-thirds immersed, and the axis is at right angles 

 to that of the succeeding turns. Post-nuclear whorls strongly 

 rounded, well constricted at the sutures; moderately slender, almost 

 vertically curved axial ribs, of wliicli 16 occur upon the first and 

 about 18 upon the rest of the turns. Intercostal spaces very broad, 

 shallow, marked by fine spiral striations. Sutures strongly con- 

 stricted. It has five post-nuclear whorls and measures: Length 2.1 

 mm., diameter 0.7 mm. 



The specimen was collected on a Chama at Mazatlan, Mexico. 



TURBONILLA (PYRGISCULUS) SWANI, new species. 

 Plate 12, figs. 9, 9a. 



Shell elongate, pupoid, semitransparent, light yellow. Nuclear 

 whorls at least two, forming a low helicoid spire, whose axis is almost 

 at right angles to that of the succeeding turns, in the first of wliich 

 it is about one-half immersed. Post-nuclear whorls inflated, very 

 strongly rounded, appressed at the summit, contracted at the periph- 

 ery, marked by strong, decidedly curved, lamellar, protractive axial 

 ribs, of which 18 occur upon all but the last whorl, the latter has 20. 

 Intercostal spaces twice as wide as the ribs, marked by 15 almost 

 equal and almost equally spaced spiral series of pits. Sutures con- 

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

 latter marked by the feeble continuations of the axial ribs, and 

 about 20 feeble very wavy incised spiral lines. Aperture oval; 

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

 within; columella slender, curved, with the posterior two-thirds 

 reenforced by the base. 



The type (Cat. no. 160485, U.S.N.M.) comes from San Pedro, 

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

 5 mm., diameter 1.5 mm. 



Named for J. G. Swan. 



Subgenus ASMUNDA Dall and Bartsch. 

 Asmunda Dall and Bartsch, Proc. Biol. Soc. Wash., vol. 17, 1904, p. 9. 



Shell with strong axial ribs which terminate at the keeled periphery; 

 base with many axial riblets, a strong median spiral cord, and a 

 constriction between this and the peripheral keel. 



Type. — Chemnitzia turrita C. B. Adams. 



