Type locality: South end of Kanaga Pass, Andreanof Ids., Aleutian Is., Alaska (51°40.0 N, 177°51.21 W), 53 m. (NMFS 95-199401-117).
Description: Shell of medium size (holotype 54.9 mm), elongated fusiform, with rounded whorls; color white; periostracum thin, yellow. Protoconch with 2.5 whorls; teleconch with six to six and a half whorls, early whorls with 11 cords, penultimate whorl with 15-17 low rounded spiral cords; base with 17-20 additional cords. Aperture about 1/3 of shell height, canal constricted, relatively long.
Radula: Typical for genus, Rachidian tooth excavated anteriorly, tricuspid, the three cusps set close together; central cusp slightly longer than the outer ones. Lateral teeth tricuspid, outer cusp long, slender, curved, central cusp much smaller, slightly curved, and slenderer, set close to inner one; inner cusp thick, curved, about 2/3 as long as outer one.
Remarks: Aulacofusus tanagaensis resembles Aulacofusus esychus (Dali, 1907), but differs in 1) Rounded as opposed to rather flattened whorls, and 2) more prominent spiral sculpture. It also resembles Aulacofusus brevicauda kurilensis Golikov & Gulbin, 1977, from the Kurile Islands, Russia, but differs in 1) much thinner shell, and 2) finer and more numerous spiral cords 15-17, as opposed to 10-12 in the former species.
Etymology: Named for Tanaga Island, where the fist specimens were collected.
Distribution: Occurs in the Andreanof Ids., central Aleutian Is., from Seguam Island (172°24 W) to West of Tanaga Island (178°07 W), at depths of 53-211 m.
Habitat: On volcanic sand and gravel bottoms, at temperatures of 3.7°- 4.8°C.