NO. 1785. WEST AMERICAN VITRINELLID8—BART8CII. 233 



whorl can be plainly seen through the substance of the last turn. 

 Periphery of the last whorl evenly rounded. Under surface broadly, 

 openly unibilicated to the very apex, well rounded from the periphery 

 to the umbilical margin. There is no limiting umbilical keel, but the 

 parietal wall bends inward with about the same curvature that it is 

 bent outside of the umbilicus. The entire under surface, including 

 that seen within the umbilicus, is marked by incised, wavy lines like 

 those on the upper surface, the whole having the same ripple-marked 

 aspect. Aperture decidedly oblique, subcircular; posterior angle 

 acute; outer lip very thin, showing the external markings within; 

 columella slender, decidedly curved; parietal wall covered with a 

 thick callus, which renders the peritreme continuous. 



The type and four other specimens of this species (Cat. No. 198904, 

 U.S.N.M.) come from the head of the Gulf of California. The type 

 measures: greater diameter, 1.3 mm. 



The species is named for Dr. William H. Dall, the honorary curator 

 of the Division of Mollusks. 



LEPTOGYRA ALASKANA Bartsch. 

 Plate 40, figs. 4-6. 

 Leptogyra alaskana Bartsch, Nautilus, vol. 23, 1910, pp. 136-7, pi. 11, figs. 4-6. 



Shell minute, depressed helicoid. Nuclear whorls one and one- 

 half, light yellow horn color, marked by faint incremental lines. A 

 single post-nuclear turn follows which is bluish-white, rather broad 

 and gently, almost evenly curved from the well-impressed suture to 

 the periphery. This whorl is marked by about twelve, fine, incised 

 spiral lines between the suture and the periphery which are stronger 

 toward the periphery than at the suture. Periphery of the last 

 whorl rounded. Base broadly and deeply unibilicated, strongly 

 arched, with a slender cord at the junction of the basal and parietal 

 wall, surface of the base marked by incised lines which are equal in 

 strength and number to those occurring upon the upper surface. 

 Wall of the umbilicus almost flat, marked by faint spiral lines. 

 Aperture very large, subcircular, posterior angle obtuse; outer lip 

 thin; columella curved, somewhat expanded and thickened basally; 

 parietal wall covered with a thin callus. Operculum thin, horny. 



Twelve specimens of this species were collected by Dr. Fred. 

 Baker at Port Graham, Alaska, four of which are in the U. S. National 

 Museum, Cat. No. 208433. One of these, the type, measures: greater 

 diameter, 0.85 mm., lesser diameter 0.7 mm., altitude 0.4 mm. The 

 remaining eight specimens are in Doctor Baker's collection. 



