76 DENTALIUM-FISSIDENTALIUM. 



narrow longitudinal ridges, not quite regular nor much projecting, 

 with slightly narrower intervals between them, all much attenuated 

 at the base, sometimes with the ribs narrower and more separated 

 at apex ; concentric growth-strioe little marked, visible especially 

 toward the base. Coloration, a yellowish-white with narrow brown 

 rings, more or less continuous, and a wide band of very deep chest- 

 nut at the base. Length 75, greatest diam. 5, curvature 5 mill. 

 (^Locard). 



The Tropics and the Sahara, in from 830 to 1113 meters. 



D. semivestitum P. Fischer, Locard, L'Echange, Revue Linne- 

 eune, xiii, No. 146, Feb., 1897, p. 9. 



D. COMPLEXUM Dall. PI. 20, fig. 25. 



Shell large, solid, thick, normally white (?), but discolored by 

 sediments after death, so that the specimens received are a pale, 

 rusty brown ; surface glossy, sharply grooved ; with wider, flat in- 

 terspaces, varying finer or coarser in different specimens; orifices 

 circular, one specimen showing indications of a wide, shallow ven- 

 tral sinus at the apex; shell little curved, and the sculpture shows 

 no rotary tendency. Length of shell 78, diameter anteriorly 8*5, 

 posteriorly 1'3, maximum divergence from a chord connecting the 

 extremities 8*5 mill. (Dall). 



Off Honolulu, Hawaiian Is., 295-298 fms. (Albatross). 



Dentalium complexum Dall, Proc. U. S. Nat. Mus., xvii, 1895, p. 

 686, pi. 26, f 3. 



This species is most nearly allied to D. candidum, but it has more 

 deeply engraved striee, and the tube tapers less. Dall writes : 



This shell differs from D. candidum Jeffreys by being more cylin- 

 drical and, so far as my present specimens go, without the long, 

 slender, ventral slit of that species. From D. ceras Watson, as fig- 

 ured, it is distinguished by being straighter and less sharply sculp- 

 tured, besides being much larger, but Watson's specimens were 

 young. With a few specimens it is easy to separate species of Den- 

 talium, but if one has numerous specimens from various kinds of 

 bottom the difficulty increases greatly. D. solidum Verrill, D. ceras 

 Watson and D. candidum Jeff'reys appear to merge into one another, 

 yet individual specimens appear very distinct when one has not a 

 connecting series. The present species, by its somewhat more cyl- 

 indrical form, seems sufficiently distinct to be named, but, with that 

 exception, is very closely related to the group of forms above enu- 



