Type locality: Stalemate Bank, W of Attu Island, Near Ids., Aleutian Is., Alaska (52°56.18 N, 170°59.19 E). 184 m (NMFS 23-199701-212).
Description: Shell large (to 143 mm, holotype), fusiform, suture deeply impressed; whorls rounded; light pink-tan, with golden-brown periostracum. Protoconch with 2.5 whorls; teleconch with 4.5 whorls. Axial ribs broadly spaced, increasing from nine in early whorls to 13 on final whorl of large specimens; ribs sometimes opisthocline (back slanted). Spiral sculpture of five to seven narrow, raised cords; interspaces variable in width, from about the same width as cords (holotype), to two to three times as wide (in paratype one), but not deeply channeled. Axial sculpture of narrow, raised growth lines. Aperture large, oval, much less than half of shell height, canal short, fairly broad.
Radula: Rachidian tooth quadrate, corners rounded. Lateral teeth tricuspid, outer cusp long, slender, tapering, constricted at the base, strongly curved distally; central cusp very small, slightly curved; inner cusp about four times as large as central one, broad, thick, strongly curved.
Remarks: Beringius undataformis differs from A. aurulentus by the prominent axial folds and the raised spiral cords (see remarks under that species).
Etymology: From the Latin undatus and forma, wavy in form, and also references its similarity to Beringius undatus DM, 1919.
Distribution: Western Aleutian Islands, known only from the Stalemate Bank, west of Attu Island (170°28 E tol71°E), atl85 m.
Habitat: Unknown, bottom temperature 3.8°C.