Description: Thallus erect to 15 cms long, branches terete with 5 - 7 pericentral cells. Corticate in the lower parts. Cystocarps barrel-shaped.

Habitat: Very rare. Epilithic, apiphytic and on artificial material at extreme low littoral and sublittoral.

Distribution: In the British Isles recorded only from Cornwall to Hampshire on the south coast of England. Recorded in Scotland however not from Ireland. Europe: Mediterranean, Portugal, Atlantic coast of Spain and France, Netherlands. Atlantic coast of North America: Canada, Maine, New Hampshire, Massachusetts, Rhode Island, Connecticut, New Jersey, Delaware, Maryland and Virginia. Further afield: the Canary Islands, Caribbean, Brazil, west Africa, Mauritius, Australia and New Zealand.

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

iNaturalist: Polysiphonia denudata at iNaturalist World Species Observations database.

WoRMS: Polysiphonia denudata at World Register of Marine Species.