Size of whole anemone rarely exceeding about 10 mm across disc or base.
Base lightly adherent, often ragged in outline due to habitual reproduction by longitudinal fission. Sometimes fission is imperfect and the anemones remain connected by a narrow strand of basal tissue.
Column not divided into regions; in extension it is cylindrical, widest at the base and disc, often kept short and almost hidden by the overhanging marginal tentacles.
Tentacles: Short or moderate in length, divided into a tapering shaft which is studded with tiny wart-like nematocyst batteries, and a well-defined acrosphere. Arrangement of tentacles as in definition Family Corallimorphidae; the exocoelic tentacles are largest and occur at the edge of the disc, the endocoelic tentacles number 3-8 on each endocoel and diminish in size inward (C. viridis tentacles).
Colouration: Very variable and often brilliant. Of the many varieties one of the commonest is bright translucent emerald green, with brown tentacle-shafts and crimson acrospheres; a marginal ring of crimson is common in this form. Other colours which may occur are white, pink, red, orange, etc., in various combinations. Usually the acrospheres are coloured differently from the tentacle-shafts which in turn contrast with the disc and column. The disc is usually plain and translucent, with the mesenteric insertions clearly visible, but in some forms it is splashed with opaque white.
On rocks, occurring on the lower shore in caves or beneath overhangs sheltered from the light. More common sublittorally, down to about 80 m, often forming dense aggregations, particularly on vertical rock faces.
Frequent to locally abundant on south and west coasts of Britain, to extreme northern Scotland, and all around Ireland. Also around south-west Europe and in the Mediterranean.