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PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXXII. 



about halfway between the two. In addition to these keels the surface 

 on the upper side is marked by many fine incremental lines and numer- 

 ous equally line spiral striations. The greatest elevation of the whorls 

 falls in the region of the middle keel, from there they slope roundedly 

 downward to tha sutural thread. Base very broadly umbillcated, 

 showing all the whorls within the umbilicus to the very apex. A 

 strong spiral keel, somewhat stronger than the peripheral one, is sit- 

 uated almost halfway between the umbilical edge and the peripher^^ 

 In addition the base is marked by fine incremental lines and scarcely 

 perceptible spiral striations. The umbilical edge is marked by a mod- 

 eratel,y strong carina and the columellar wall, which is moderateh^ 

 rounded, bears immediately below this three equally spaced threads, 

 the outer two of which are as strong as the carina at the edge, while 

 the inner one is only feebly developed. Aperture extremely oblique, 

 pentagonal, the angles being formed by the keels, the posterior angle 

 of the aperture and the umbilical carina; outer lip thin; columella 

 strongl}' curved; parietal wall with a faint callus. 



Fig. 9.— Circulus cerrosensis. a, top view; b, side view; c, basal view. 



The type and only specimen known. Cat. No. 151942, U.S.N.M., 

 was dredged by the U. 8. Bureau of Fisheries Steamer Albatross at 

 Station 2827 ofi' Cerros Island, Lower California, in 10 fathoms of 

 water. It has 5 whorls and measures: Greater diameter, 2.5 mm.; 

 lesser diameter, 2.1 mm.; altitude, 1.1 mm. 



While this specimen resembles C. cosrnius closely in general outline, 

 it can nevertheless be distinguished quite readily hy the fine spiral 

 sculpture between the keels on the upper surface, which is absent in 

 C. cosrnius and by the much more strongly developed spiral cords on 

 the columellar wall of the umbilicus. 



CYCLOSTREMELLA CALIFORNICA, new species. 



Shell small, planorboid, semitransparent, closel}' spirally striated. 

 Nepionic whorls li, moderately rounded, smooth and shining. Suc- 

 ceeding turns increasing regularly in size like Plauorbis, rendering 

 the apex considerably lower than any of the succeeding turns, the last 

 being the most elevated. Whorls well rounded, separated by strongly 

 impressed sutures and mai'ked by many equally strong and equallj" 



