Distribution. Oregon, 43°25.0' to 45°54.1* N and 124°46.0' to 125°01.1' W, living at 347-800 m.
Description. Shell medium sized for genus, up to 22.8 mm in length (holotype), length/width ratio 2.1-2.3. Shape slender, broadly ovate, lightly built, tuberculate; subsutural ramp broad, weakly sloping, convex. Shell color entirely white. Spire high, teleoconch up to five broad, convex, weakly angulate, weakly shouldered, nodose whorls; suture impressed. Protoconch, early teleoconch whorls eroded or broken in all examined specimens. Axial sculpture of teleoconch whorls consisting of low, narrow, diagonally slanted ribs, occasional growth lamellae. Last whorl with 14-18 ribs; penultimate, antepenultimate whorls with 12—13 ribs. Spiral sculpture of low, weak, primary cords, last teleoconch whorl with five cords (P1-P5), penultimate with visible P1-P3. Axial ribs, spiral cords forming small knobs at intersection. Aperture large, broadly ovate; columellar lip narrow, smooth, rim adherent. Outer lip smooth, thin, interiorly smooth. Siphonal canal long, narrow, twisted, broadly open ventrally. Operculum dark brown, ovate, with apical nucleus.
Remarks. Boreotrophon tripherus Dall, 1902 has no spiral cords, no beaded intersection with axial sculpture, and has a narrower and less rounded profile of the final whorl. Boreotrophon disparilis (Dall, 1891) has more numerous diagonally slanted axial ribs and less obvious nodes at intersection of axial ribs and spiral cords, and has an obviously broader, more globose last teleoconch whorl.
Etymology. Pseudo (G) = false. Named for its resemblance with Boreotrophon tripherus.