138 TIIK NAUTILUS. 



Onoba asser, new species. PI. XI, fig. 9. 



Shell elongate conic, bluish white, semitranslucent. Nuclear 

 whorls one and one-tenth, smooth, a little less elevated than the suc- 

 ceeding turns. Post-nuclear whorls very iiigh between the sutures, 

 orerhanging, moderately rounded, appressed at the summit. The 

 preceding wliorl shines through tlie summit of the succeeding turn 

 and gives this the appearance of having a double suture. Sutures 

 well impressed. Periphery of the last whorl well rounded. Base 

 moderately prolonged, well rounded. Entire surface of spire and 

 base marked by closely placed exceedingly fine microscopic spiral 

 striations. Aperture very broadly ovate, posterior angle obtuse, 

 outer lip thin ; peritreme complete. 



The type, cat. no. 208434 U. S. N. M., was collected by Dr. 

 Fred 15aker at Fort Graliam, Alaska. It has four and a half whorls 

 and measures : length 2.2 mm., diameter .9 mm. This species is 

 nearest related to Onoha cerineUa Dall, from which it is distinguished 

 by its lesser size and more delicate structure. 



Odostomia (evalea) cookeana, new species. PI. XI, fig. 7. 



Shell elongate ovate, very narrowly umbilicated, yellowish white. 

 Nuclear whorls very obliquely immersed in the first of tlie succeed- 

 ing turns. Post-nuclear whorls very high between the sutures where 

 they are very moderately rounded and marked by ratlier strong in- 

 cremental lines and very numerous fine spiral striations. Periphery 

 and base of the last whorl somewhat inflated, the latter strongly 

 rounded and marked like the spire. Aperture large, oval ; posterior 

 angle acute; outer lip thin; columella decidedly oblique, quite 

 strongly curved in the middle and somewhat reflected, provided with 

 an oblique fold at its insertion which is strong within and tapers to a 

 vanishing point at the free edge of the columella ; parietal wall glazed 

 with a thin callus. 



Two specimens of this species were collected by Dr. Baker at 

 Ellamar, Alaska. One of these, an immature specimen, furnished 

 our description of the nucleus, the other, cut. no. 208427 U. S. N. 

 M., gave the adult characters. The adult specimen has its nucleus 

 badly eroded. The four remaining whorls measure : length 3.2 mm., 

 diameter 2.0 mm. The young individual which is in Dr. Baker's 

 collection has ?\ whorls and measures : length 2.3 mm., diameter 

 1.4 mm. 



Named for Miss J. M. Cooke of San Diego at the request of Dr. 

 Baker. 



