MUSEUM OF COMPARATIVE ZOOLOGY. 37 



This superb species may be compared with D. aciUusimum Watson, but is 

 proportionally more slenuer, wants the I'uint longitudinal strise, and is without 

 an anal notch on the concave side. 



D. agile M. Sars. 

 Anlalis agilis G. 0. Saks, Moll. Reg. Arct. Norv., p. 102, tab. 20, fig. 9. 1878. 



Station 32, 804 fms. Station 33, 1,568 fms. 



I can find no characters to separate these specimens from Sars's species, 

 except the absence of the (inconstant) notch at the anal extremity, although 

 they appear to be perfect. 



D. antillarum D'Orb. 



Sagra, Moll. Cub., ri. XXV. figs. 10-13. 



Station 20, 220 fms. ; Barbados, 100 fms. ; Yucatan Strait, 640 fms. ; Sta- 

 tion 44, 539 fms. ; Station 19, 310 fms. ; Station 43, 339 fms. ; Station 33, 

 1,568 fms. ; off C. San Antonio, 1,002 fms. 



D. disparile D'Orb. 



Loc. cit., figs. 14-17. 

 Station 41, 860 fms.; Yucatan Strait, 640 fms.; Barbados, 100 fms. 



D. ceras "Watson. 



Station 33, 1,568 fms. 



This specimen measures 50.0 mm. in length, "Watson's came from the mid- 

 Pacific, east of Japan, in 2,050 fms., and from the Atlantic, west of Valparaiso, 

 in 2,160 fms. 



D. sericatum n. s. 



Shell small, very thin, acute, slightly curved, rather rapidly enlarging ; cov- 

 ered with fine, sharp, close set longitudinal grooves with narrower threadlike 

 interspaces separating them to the number of thirty-six on the middle and 

 about fii'ty at the oral end of the shell ; plane of the oral aperture at right 

 angles to the axis, both apertures circular, simple ; color translucent white, 

 with opaque white wavy lines (like those on the silk goods known as moire 

 antique) encircling the shell with zigzags whose successive irregular bands 

 (0.8 mm. apart in the middle of the shell) are sub-parallel with one another, 

 and gradually become more slender and further apart toward the ends. In a 

 specimen 13.0 mm. long there are about fifteen of these bands, each band 

 with about 10 or 12 angles. Lon. 13.0. Anal diam. 0.37. Oral diam. 

 1.2 mm. 



Yucatan Strait, 640 fms. 



