WEST AMERICAN PYKAMIDELLID MOLLUSKS. 97 



one-fifth immersed. Post-nuclear whorls slightly rounded on the 

 anterior two-thirds between the sutures, posterior third forming a 

 strong sloping shoulder, marked by narrow, lamellar ribs, of which 

 18 occur upon the first, 16 upon the second to seventh, and 18 upon 

 the eighth and penultimate turn. Intercostal spaces about four 

 times as wide as the ribs, marked by a double series of pits, one of 

 which is at the periphery and the other at the angle of the shoulder. 

 The space between the two pits is crossed by nine equal and equally 

 spaced spiral striations, the space between the summit and the sub- 

 median pit is marked by twelve incised spiral lines of which those 

 near the summit are finer and closer spaced than the rest. Sutures 

 strongly impressed. Periphery of the last whorl slightly angulated. 

 Base short, well rounded, marked by about twenty equal and almost 

 equally spaced spiral striations. Aperture rhomboidal; posterior 

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

 columella slender, almost straight and somewhat revolute. 



The type and another specimen (Cat. no. 162428, U.S.N.M.) was 

 dredged at U. S. Bureau of Fisheries station 2799, in Panama Bay, 

 in 29^ fathoms. It has nine post-nuclear whorls and measures: 

 Length 5.2 mm., diameter 1.5 mm. 



TURBONILLA (PYRGISCUS) SmMEKI, new species. 



Plate 9, figs. 4, 4a. 



Shell elongate-conic, with a very large nucleus which extends be- 

 yond the outline of its post-nuclear spire; bluish- white with four 

 rather broad, pale yellow bands, one of which is immediately below 

 the summit and another at the periphery, a third halfway between 

 the two, while the fourth is on the middle of the base. Nuclear 

 whorls one and one-half, planorboid, having their axis at right angles 

 to that of the succeeding turns, upon the first of which it rests. Post- 

 nuclear whorls somewhat overhanging, appressed and slightly ex- 

 serted at the summit, well rounded, the greatest convexity falUng 

 on the anterior third between the sutures, marked by broad, low, 

 rounded, slightly retractive axial ribs on all but the first two whorls, 

 which are smooth. Of these ribs, 14 occur upon the third to sixth, 

 16 upon all the remaining whorls excepting the penultimate, which 

 has 18. Intercostal spaces shallow, almost twice as wide as the ribs, 

 marked by nineteen series of incised spiral pits, of which the periph- 

 eral and the sixth below the summit are a little stronger than the 

 rest. Sutures well impressed. Periphery and base of the last whorl 

 well rounded, marked by the continuations of the axial ribs and spiral 

 lines like those between the sutures. Aperture moderately large, 

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

 markings within; columella slender, flexuose, and slightly revolute. 



