Diagnosis. Shell large, siphonal canal short; growth determinate, aperture slightly thickened and projecting in mature shell; periostracum thin to relatively thick, flaking, adherent, or laminate. Protoconch, usually large, of several strongly projecting whorls that only slightly increase in diameter. Operculum, large, dull, concave, with terminal nucleus, filling aperture when animal is retracted. Radula: Rachidian tooth reduced to a simple, acuspate plate. Egg capsules (of Beringius) large, up to 40 x 47 mm, oval, flap-like, attached to the substrate along the bottom edge, and deposited in rows. Capsules bearing 1– 4 juveniles at hatching.
Remarks: In the Aleutian Islands, 18 species four genera are recognized, including 11 species and two genera new to science.