Description: Gametangial phase much branched, to 20 cms in length. Branches spirally in pairs of unequal length. Some branches form reflexed hooks by which it attaches itself to other algae. The tetrasporangial phase Trailliella is monosiphonous, irregularly branched and although only a few cms long is readily identified by the small colourless cell at the upper end, and set to the side, of each cell.

Habitat: Gametangial phase usually sublittoral or occasionally low littoral. Tetrasporangial phase usually epiphytic in lower littoral and sublittoral to 8 m.

Distribution: British Isles: England, except on the east coast, Ireland, Scotland, Wales, Isle of Man and the Channel Islands. Europe: Mediterranean, Atlantic coasts of Spain and France, Netherlands (drift), Helgoland, Baltic Sea, Norway, the Faroes and Iceland. Atlantic coast of North America: Canada, Maine, New Hampshire, Massachusetts, Connecticut, Long Island and Virginia. Further afield: Canary Islands, South Africa and Japan.

Key Identification Features:

• Gametangial phase shows some branches forming reflexed hooks. Tetrasporangial phase shows colourless cells at the upper end of each cell.

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

iNaturalist: Bonnemaisonia hamifera at iNaturalist World Species Observations database.

WoRMS: Bonnemaisonia hamifera at World Register of Marine Species. Accepted name: Bonnemaisonia hamifera Hariot, 1891. AphiaID: 144442.

Classification: Biota; Plantae; Biliphyta; Rhodophyta; Eurhodophytina; Florideophyceae; Rhodymeniophycidae; Bonnemaisoniales; Bonnemaisoniaceae; Bonnemaisonia