232 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.39. 



numerous, exceedingly fine, retractive lines of growth, and very 

 many, exceedingly fine, closely-spaced, spiral striations. Under 

 surface broadly, openly umbilicated, moderately rounded, the 

 umbilical edge being bounded by a slender thread; entire surface 

 marked like the upper surface. Aperture subcircular; outer lip 

 rendered } -shaped by the peripheral keel; columella short, strongly 

 curved, with a strong cord in the middle of the umbilical side. 



Two specimens of this species (Cat. No. 211800, U.S.N.M.) were 

 dredged at U. S. Bureau of Fisheries station 2822, in 21 fathoms, 

 on gray sand and broken shell bottom, off La Paz, Gulf of California. 

 The larger of these, the type, has one and a third post-nuclear whorls 

 and measures: greater diameter, 1.6 mm. 



CIRCULUS DIOMEDE^, new species. 

 Plate 40, figs. 1-3 



Shell small, planorboid, creamy-white. Nuclear whorls two and a 

 half, regularly coiled, forming a depressed spire, with the whorls well 

 rounded and smooth, separated by a well-impressed suture. Post- 

 nuclear whorls appressed at the summit, the appressed portion forming 

 a slender, spiral thread, with a slender, acute keel at the periphery, 

 the space between the peripheral keel and the thread at the summit 

 being evenly curved and smooth, except for the decidedly retractivch' 

 curved, faint, incremental lines. Under surface very broadly, openly 

 umbilicated, and evenly curved from the peripheral keel to within 

 the umbilicus; marked by incremental lines only. Within the um- 

 bilicus all of the preceding whorls are visible to the very apex. 

 Aperture decidedly oblique, subcircular; posterior angle acute; 

 outer lip thin, rendered } -shaped by the peripheral keel; columella 

 slender, decidedly curved; parietal wall covered with a thick callus, 

 which renders the peritreme complete. 



The type and three additional specimens of this species were 

 dredged by the U. S. Bureau of Fisheries' steamer Albatross at station 

 2794, in 62 fathoms, on gray sand and broken sliell bottom; bottom 

 temperature 59.6°; in the Bay of Panama. The type measures: 

 greater diameter, 2.2 mm. 



CYCLOSTREMELLA DALLI, new species. 

 Plate 40, figs. 10-12. 



Shell very small, depressed, helicoid, subdiaphanous. Nuclear 

 whorls two and a half, well rounded, separated by a well-impressed 

 suture, smooth. Post-nuclear whorls one and an eighth, evenly 

 rounded from the impressed suture to the periphery; marked by 

 numerous, irregular, wavy, incised, spiral lines, which lend the entire 

 surface a ripple-marked aspect. On the upper surface the preceding 



