Shell frequently colored, with cone-shaped, moderately elevated spire and heterostrophic embryonic shell; last whorl fairly large, oval, often with spiral rows of punctures; aperture moderately long, narrow above, roundly expanded below; columellar margin in most cases with one fold.
The buccal armature of the animal consists of very small structures which are cuspidate on the margin; radula broad, with extremely small and numerous plates, which consist of a posteriorly pointed base and a broad, somewhat denticulate, half-moon-shaped cutting edge. Species without columellar fold are to be separated as the subgenus or perhaps genus Metactaeon. A. (M.) aequatorialis Thiele.
Synonyms Tornatella Lamarck, 1812; Speo Risso, 1826.