WEST AMERICAN PYKAMIDELLID MOLLUSKS. 99 



whorls moderately rounded, widest a little above the suture, sloping 

 gently toward the summit and more abruptly toward the base, orna- 

 mented by moderately strong, rounded, somewhat flexuous, axial 

 ribs, of which about 18 appear upon the second, 20 upon the seventh, 

 22 upon the eighth, and 27 upon the penultimate whorl. Intercostal 

 spaces only moderately deep, a little wider than the ribs, marked by 

 6 strong incised spiral lines which extend up on the sides of the ribs 

 and frequently pass over their summits; the uppermost or posterior 

 one of these incised lines is least pronounced, the second one above 

 the suture, and the third one about half again as far apart as the 

 remaining, which are ecpially spaced. In addition to these the shell 

 is marked by many faint wavy spiral striations between the deep 

 ones. Sutures plain, well defined. Base of the last whorl very 

 short, well rounded, marked by the faint continuations of the axial 

 ribs and about 15 well defined more or less equally spaced deep spiral 

 striations with fainter ones between them as on the exposed portion 

 of the whorls of the spire; the first deep basal spiral striation and the 

 one above the suture are some little distance apart and mark a plain 

 band excepting the fainter sculpture. Aperture quite large, sub- 

 quadrate; columella short, somewhat twisted, revolute. 



The type (Cat. no. 162679, U.S.N.M.) was dredged by the U. S. 

 Bureau of Fisheries steamer Albatross at station 2902, off Santa 

 Barbara, California, in 53 fathoms. It has 12 post-nuclear whorls 

 which measure: Length 11.2 mm., diameter 2.8 mm. 



Another specimen (Cat. no. 162680, U.S.N.M.) was dredged at 

 station 3195, in 252 fathoms, on green mud, bottom temperature 

 43°. 2, in San Luis Obispo Bay, California. Four specimens (Cat. no. 

 1 6268 1) were dredged at station 2901, on gray sand and mud bottom, 

 at a depth of 48 fathoms, temperature 55°. 1, off Santa Rosa Island. 

 The University of California has two lots, one specimen dredged at 

 station 32, off Catalina Island, and two from station 59, off San 

 Diego, California. 



TURBONILLA (PYRGISCUS) HALIDOMA, new species. 

 Plate 9, figs. 6, 6rt. 



Shell elongate-conic, milk-white. Nuclear whorls small, two and 

 one-fourth, forming a moderately elevated spire whose axis is at 

 right angles to that of the succeeding turns, in the fii"st of which it is 

 about one-fourth immersed. Post-nuclear whorls flattened in the 

 middle, with a sloping shoulder that extends over the posterior 

 fourth between the sutures and renders the whorls slightly angulated 

 at their anterior margin; weakly contracted at the suture, marked 

 by moderately strong, well rounded, low, retractive axial ribs, of 

 which 24 occur upon the first, 26 upon the second and third, and 24 

 upon the remaining turns. Intercostal spaces a little more than 



