Shell trochiform, more or less flattened below, sometimes depressed above; the young shell is always carinated and spinose at the margin; operculum oval or oblong, with generally submarginal or terminal multispiral nucleus, usually with one to several external ribs.

Astralium Link, 1807, p. 135 (type species (monotypy): Astralium deplanatum Link, 1807 = Turbo calcar Linne, 1758) is a low-spired to very high-spired group having sculpture of major radial folds or ribs which are sometimes produced into short spines, a completely closed umbilicus, a flat, smooth operculum, and the basal callus usually narrow and separated from the columella. Genus-group names that may be synonyms of Astralium or may in some cases prove to be subgenera are: Calcar Montfort, 1810, p. 135 (type species (by monotypy): Calcar sporio Montfort, 1810 = Turbo calcar Linne', 1758); Cyclocantha Swainson, 1840, p. 348 (type species (by subsequent designation, herein): Turbo calcar Linne, 1758); Stella Herrmannsen, 1849, p. 501 (type species (by original designation): Trochus Stella Lamarck, 1822); Distellifer Iredale, 1937, p. 249 (type species (by original designation): Distellifer wallisi Iredale, 1937, = Trochus rhodostomus Lamarck, 1822); Pagocalcar Iredale, 1937, p. 249 (type species (by original designation): Trochus pileolum Reeve, 1842, ? = Trochus limbiferus Kiener, 1850); Rugastella Iredale, 1937, p. 249 (type species (by original designation): Trochus rotularius Lamarck 1822); Bellastraea Iredale, 1924, p. 232 (type species (by original designation): Bellastraea kesteveni Iredale, 1924); Micrastraea Cotton, 1939, p. 169 (type species (by original designation): Trochus aureus Jonas, 1844).