Description: Thallus erect, growing to 20 cms long, cylindrical with whorl-branching. Densely clothed with imbricate whorls which devide 1 - 3 times.

Habitat: Epilithic in rock pools in the lower littoral and sublittoral to 14 m.

Distribution: Common in the British Isles specially in the south-west, rarer in Scotland and the east coast of England. Europe: Portugal, Spain and France. Further afield: Canary Islands, Mauritania and Argentina.

Similar Species: Dasya hutchinsiae and Aglaothamnion sepositum these have spiral rather than whorled branchlets. Sphondylothamnion multifidum has widely spaced whorls.

Key Identification Features:

• Dense overlapping whorls.

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

iNaturalist: Halurus equisetifolius at iNaturalist World Species Observations database.

WoRMS: Halurus equisetifolius at World Register of Marine Species.