Description: Fronds filiform, branching to 70 cms long and up to 3 mm in diameter and solid. With long simple branches. The cortex is of very small assimilatory filaments only a few cells long and not arranged in whorls with gelatinous hairs. Slimy.

Habitat: Common as a summer annual in then lower littoral and sublittoral.

Distribution: Widely distributed in the British Isles. Europe: Mediterranean, France, Baltic Sea, Norway, Faroes, Iceland. Atlantic coast of North America: Canada, Maine, Connecticut and Long Island. Further afield: Arctic Seas: Spitzbergen, the Murman Sea, White Sea, Siberian Sea, Baffin Bay on the west coast of Greenland, Japan and China.

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

iNaturalist: Chordaria flagelliformis at iNaturalist World Species Observations database.

WoRMS: Chordaria flagelliformis at World Register of Marine Species. Accepted name: Chordaria flagelliformis (O.F.Müller) C.Agardh, 1817. AphiaID: 144910.

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