Description: Thallus forming small spots up to 1 mm in diameter. At the periphery monostromatic branches radiate out, in the centre the cells form small erect unbranched filaments of 4 - 12 cells long closely packed in a turf-like manner.

Habitat: Very rare. Epiphytic on Zostera in the lower littoral and upper sublittoral.

Distribution: Generally distributed around the British Isles including the. Europe: Mediterranean and the Black Sea, Portugal, Spain, France, Belgium, Netherlands, Denmark, Baltic, Sweden and Norway. Atlantic coast of North America: Canada, Maine, New Hampshire, Massachusetts, Rhode Island and Virginia. Further afield: Canary Islands, California on the Pacific coast of the U.S.A. and West Africa.

Similar Species: There are a number of similar species growing as epiphytes or epilithic - all very small and difficult to identify. Microscopic examination is required.

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

iNaturalist: Myrionema magnusii at iNaturalist World Species Observations database.

WoRMS: Myrionema magnusii at World Register of Marine Species. Accepted name: Myrionema magnusii (Sauvageau) Loiseaux, 1967. AphiaID: 156254.

Classification: Biota; Chromista; Harosa; Heterokonta; Ochrophyta; Phaeophyceae; Fucophycidae; Ectocarpales; Chordariaceae; Myrionema