WEST AMEKICAN PYRAMIDELLID MOLLUSKS. 119 



TURBONILLA (MORMULA) IGNACIA, new species. 

 Plate 11, figs. 2, 2a. 



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

 one-half, forming 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-fifth immersed. Post-nuclear whorls slightly rounded, appressed 

 at the summit, moderately contracted at the suture, marked by low, 

 rather broad, rounded, almost vertical axial ribs, of which 18 occur 

 upon the second to fourth, 20 upon the fifth, 22 upon the sixth, 24 

 upon the seventh, and 28 upon the penultimate turn. Intercostal 

 spaces a little narrower than the ribs, marked by six spiral series of 

 well incised, equally spaced pits. Peri])hery and base of the last 

 whorl well rounded, marked by the very feeble continuations of the 

 axial ribs, and numerous exceedingly fine spiral striations. Aper- 

 ture rhomboidal; posterior angle obtuse; outer lip thick, reenforced 

 by two strong spiral lamellae, one of which is a little posterior to the 

 periphery and the other a little posterior to the middle between the 

 periphery and the summit ; columella rather strong, decidedly twisted 

 with an oblique fold a little below its insertion. 



The type and two other specimens (Cat. no. 162691, U.S.N.M.) 

 comes from San Ignacio Lagoon, Lower California. The type has 

 nine post-nuclear whorls and measures: Length 4.1 mm., diameter 

 1.2 mm. 



TURBONILLA (MORMULA) PERISCELIDA, new species. 

 Plate 11, figs. 6, 6a. 



Shell pupiform, milk-white, shining. Nuclear whorls small, two, 

 forming 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 flattened, slightly contracted at the 

 sutures, appressed at the summit, with a strong, sloping shoulder 

 which extends over the posterior fourth of the space between the 

 sutures, marked by strong, vertical axial ribs, of which about 14 

 occur upon all the whorls. These ribs become flattened and decid- 

 edly expanded on the shoulder. Intercostal spaces about three times 

 as wide as the ribs, shallow, smooth. Sutures slightly constricted. 

 Periphery of the last whorl somewhat attenuated, base well rounded, 

 smooth. Aperture oval; somewhat effuse anteriorly; posterior angle 

 acute; outer lip reenforced by three, broad, internal s]>iral lirations, 

 two of which are posterior to the periphery and the other immediately 

 below it; columella decidedly twisted and somewhat re volute; reen- 

 forced by the base, provided with a very strong, oblique fold at its 

 insertion; parietal wall covered by a thin callus. 



The type and two specimens (Cat. no. 163266, U.S.N.M.) were 

 dredged at U. S. Bureau of Fisheries station 2901, off Santa Rosa 



