Description: Thallus small of dense mats to 2 cm thick of prostrate and erect polysiphonous terete axes of 10 to 19 periaxial cells, ecoticate.

Habitat: Very rare. Epilithic and on Fucus vesiculous holdfasts in the upper intertida; and at low water.

Distribution: Southerly coasts of the British Isles. England: Cornwall, Devon and Dorset. Ireland: Galway and Cork also the Channel Islands. Europe: Black Sea and Mediterranean. Further afield: Bermuda, Florida, West Indies, Red Sea and the Pacific Ocean.

Similar Species: Polysiphonia atlantica, P. devoniensis and P. stricta but Lophosiphonia has has a large number of periaxial cells.

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

iNaturalist: Lophosiphonia reptabunda at iNaturalist World Species Observations database.

WoRMS: Lophosiphonia reptabunda at World Register of Marine Species.