170 BULLETIN 68, UNITED STATES NATIONAL MUSEUM. 



spaced incised lines, the s])ace between the summit and the first line 

 below it appearing as a thickened cord. Sutures well impressed. 

 Periphery of the last whorl and base well rounded, marked by the 

 strong continuation of the axial ribs and about five incised spiral lines. 

 Aperture ovate; posterior angle acute; outer lip thin, showing the 

 external sculpture within; columella stout, slightly curved and some 

 what revolute; parietal wall covered by a very strong callus. 



Professor Adams's type, wliicli comes from Panama, has served for 

 our description and figure. It is at Amherst College. It has six and 

 one-lialf post-nuclear whorls and measures: Lengtli 2.8 mm., diam- 

 eter 1.1 mm. 



Subgenus EGILA Dall and Bartsch. 



Egila Dall and Bartsch, Proc. Biol. Soc. Wash., vol. 17, 1904, p. 11. 



Odostomias with the axial ribs extending from the summit of the 

 whorls to the umbilical region; periphery with a deep sulcus bounded 

 on each side by a tumid area; the base is spirally striated. 



Type. — Parthenia lacunata Carpenter. 



KEY TO THE SPECIES OF THE SUBGENUS EGILA. 



Axial ribs about 18 upon the'last whorl lacunata. 



Axial ribs about 30 on the last whorl poppei. 



ODOSTOMIA (EGILA) LACUNATA Carpenter. 



Plate 19, fig. 1. 



Parthenia lacunata Carpenter, Cat. Mazatlau Shells, 1856, p. 414. 



Shell small, oval, white. Nucleus almost completely obliquely 

 immersed in the first of the succeeding turns. Post-nuclear whorls 

 flattened, with subtabulated summits and deeply sulcated periphery, 

 marked by sublamellar, slightly retractive axial ribs, of which 14 

 occur upon the first and second and 18 upon the penultimate turn. 

 Intercostal spaces three times as wide as the ribs, smooth. Periphery 

 deeply and broadly sulcate, bordered on each side b}^ a low spiral 

 cord, crossed by the continuations of the axial ribs. Base of the 

 last whorl well rounded, marked by the axial ribs which continue 

 almost undiminished to the umbilical chink and about twelve spiral 

 lirations. Aperture oval; posterior angle obtuse; outer lip thin, 

 showing the external sculpture within; columella slender, curved, 

 and slightly revolute; parietal wall covered by a thin callus. 



Doctor Carpenter's type, which is on tablet 1964 Liverpool collec- 

 tion, British Museum, and six specimens were taken from Sj)ondylus 

 at Mazatlan, Mexico. The type has four post-nuclear turns and 

 measures: Length 1 mm., diameter 0.57 mm. 



ODOSTOMIA (EGILA) POPPEI, new species. 

 Plate 19, fig. 3. 

 Shell elongate-ovate, milk-white. Nuclear whorls small, com- 

 pletely obliquely immersed in the first post-nuclear turn above 

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



