Description: Thalli growing from a small diuscoid holdfast to 1.5 m in length. Cylindrical, hollow of uniform diameter, cord-like and unbranched. Tough, slimy and densely covered with long fine hair-like filaments.

Habitat: Rare. Epilithic to 25 m depth.

Distribution: A northern species in the British Isles recorded from the west and north of Ireland, Isle of Man and Scotland. Europe: France, Baltic Sea, Sweden, Norway, Faroes, Jan Mayen and Bjornoya, Spitzbergen and Iceland. Greenland. Atlantic coast of North America: Canada Maine, New Hampshire, Massachusetts, Rhode Island, Connecticut and Long Island.

Similar Species: Chorda filum. The thalli of Halosiphon are, however, shorter and are densely covered with filaments, the thalli of Chorda are not so densely covered and the filaments are deciduous.

Key Identification Features:

• Unbranched and densely covered with coloured filaments.

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

iNaturalist: Chorda tomentosa at iNaturalist World Species Observations database.

WoRMS: Chorda tomentosa at World Register of Marine Species. Accepted name: Halosiphon tomentosus (Lyngbye) Jaasund, 1957. AphiaID: 145723.

Classification: Biota; Chromista; Harosa; Heterokonta; Ochrophyta; Phaeophyceae; Fucophycidae; Chordales; Chordaceae; Chorda