Milne-Edwards and Haime, 1848
Corallum: Solitary, free, wedge-shaped and laterally compressed, up to 10 mm high. Septa regularly arranged in three cycles, 6 + 6 + 12, exsert; costae prominent, some of them converging on the lower part of the corallum. Columella forming a single vertical lamella in line with the long axis of the calyx, sometimes divided into two or three aligned plates. Pali are absent. Shape of young specimens, up to about 2 mm in height and diameter, usually less elongated and more nearly cylindrical or sub-spherical with the calyx circular, not laterally compressed. In these only the first two cycles of septa may be developed and the columella may be absent or consist of only a few rudimentary papillae. Such young are often bipolar, with a calyx at each end, in correlation with transverse fission.
Polyp: Up to 24 knobbed tentacles are present; details of colouration, if any, are not recorded.
Lives interstitially in coarse sand or shell gravel from the shallow sublittoral (c. 9 m) down to at least 100 m depth.
Recorded sporadically from all coasts of British Isles, probably not uncommon but easily overlooked due to its small size. Further distribution includes all south-west coasts of Europe, Madeira and Azores, the Mediterranean, and west Africa from Morocco to Senegal.