Genus Acasta Leach, 1817

Type species. Lepas spongites Poli, 1791, by original designation.

Diagnosis. Basis deeply cup shaped, rarely flat, with circular margin, often bearing small teeth; internal surface smooth, without six radial ribs. Wall plates usually with longitudinal, internal ribs; in some species, wall plates separated by splits or windows covered by delicate membrane. Carinolaterals developed normally. Scutum with or without radial striae. Cirral armature variable, segments of anterior ramus of cirrus IV bearing hooks, or thorns, or lacking either (after Kolbasov 1993).