Diagnosis: Shell small to large (4–16 cm), periostracum thin or lacking; aperture large. Protoconch usually large, bulbous; aperture 1/2 to 3/4 of shell height; sculpture of spiral cords or lirae, axial sculpture usually absent, if present of, folds or wrinkles, varices rare. Radula: Rachidian tooth with 2–7 cusps, lateral teeth with 2, rarely 3 cusps. Operculum much smaller than aperture. Egg cases dome-like or semi-spherical, with typically two to four juveniles.
Remarks: In the Aleutian Islands, 13 species in four genera are recognized, including three new species and one new genus.