Description: Microscopic filamentous thalli, creeping superfically in other algae. Irregularly branched with erect bulb-shaped cells tapering to form a slender hair 0.8 mm maximum length.

Habitat: Probably common. Endophytic in or in other algae. Littoral rock pools and sublittoral.

Distribution: British Isles including the Shetlands. Europe: Spain, France, Netherlands, Baltic Sea, Norway, Faroes, Finland and Iceland. Greenland. Atlantic coast of North America: Canada, Long Island to Maine, New Hampshire, Massachusetts, Rhode Island, Connecticut and Texas. Further afield: the White Sea in the Arctic and the Pacific coast of North America.

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

iNaturalist: Bolbocoleon piliferum at iNaturalist World Species Observations database.

WoRMS: Bolbocoleon piliferum at World Register of Marine Species.