WEST AMERICAN PYRAMIDELLID MOLLUSKS. 179 



ODOSTOMIA (MIRALDA) GALAPAGENSIS, new species. 



Plate 19, fig. 7. ■ 



Shell conic, milk-white. Nuclear whorls at least two, forming a 

 depressed helicoid spire, which is slightly tilted to one side and for 

 the greater part immersed in the first of the succeeding turns. The 

 tilted edge of the nucleus shows traces of spiral lirations. Post- 

 nuclear whorls appressed at the summit, ornamented by two very 

 strong, lamelliform keels, whose edges are decidedly upturned, forming 

 deeply channeled troughs. The posterior of the two lamellae is feebly 

 crenulated. Periphery of the last whorl marked by a spiral keel 

 which is about half as strong as those between the sutures. A fourth 

 keel, a little weaker than the peripheral one, marks the middle of 

 the base. The deep concave channels between the keels are marked 

 by strong lines of growth. Sutures strongly channeled. Aperture 

 irregularly oval ; posterior angle obtuse; outer lip rendered angular by 

 the spiral keels; columella stout, curved, reenforced by the base; 

 parietal wall covered with a thin callus. 



The type (Cat. no. 206906, U.S.N.M.) was dredged at U. S. Bureau 

 of Fisheries station 2813, in 40 fathoms, on coral sand bottom, near 

 the Galapagos Islands. It has six post-nuclear whorls and measures: 

 Length 2.0 mm., diameter 0.8 mm. 



Subgenus IVARA Dall and Bartsch. 



Ivara Dall and Bartsch, Mem. Cal. Acad., vol. 3, 1903, p. 285; Proc. Biol. Soc. 

 Wash., vol. 17, 1904, p. 11. 



Odostomias having feebly developed axial ribs which are usually 

 onl}" indicated near the summits of the whorls; spiral sculpture con- 

 sisting of many subequaily spaced fine lirations; summits of the 

 whorls strongly tabulated. 



Type. — Odostomia (Ivara) turricula Dall and Bartsch. 



ODOSTOMIA (IVARA) TURRICULA Dall and Bartsch. 



Plate 19, fig. 9. 



Odostomia (Ivara) terricula (misprint for turricula) Dall and Bartsch, Mem. Cal. 

 Acad. Sci., vol. 3, 1903, p. 285, pi. 4, fig. 14. 



Shell very elongate-ovate, milk-white. Nuclear whorls smooth, 

 obliquely immersed in the first of the succeeding turns, above which 

 only the tilted edge of the last volution projects. Post-nuclear 

 whorls moderately rounded, very broadly tabulately shouldered at 

 the summit, moderately contracted at the peripherv, marked by 

 low, feebly developed axial ribs, which are best shown at the angle of 

 the shoulder and scarcely extend to the suture. In addition to the 

 axial ribs, the whorls are marked by well-incised spiral lines, of which 

 7 occur between the sutures on the second and 9 upon the third and 

 the penultimate turn. Periphery and base of the last whorl well 



