Description: Thallus uniseriate, erect to 5 cm long. Finely branched with corticating filaments.

Habitat: Epiphytic and epilithic, sublittoral to 12 m deep.

Distribution: Widely distributed in the British Isles. Europe: Mediterranean, Portugal, Atlantic coasts of Spain and France, Baltic Sea, Netherlands, Norway, Faroes, Spitzbergen and Iceland. Greenland. Atlantic coast of North America: Canada and New Hampshire, Massachusetts, Rhode Island, Connecticut and Virginia. Further afield: Jamaica and Canary Islands, generally worldwide.

Similar Species: The different species of Callithamnion and Aglaothamnion are very similar.

Distribution Map from NBN: Callithamnion corymbosum at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Callithamnion corymbosum at iNaturalist World Species Observations database.

WoRMS: Callithamnion corymbosum at World Register of Marine Species.