Description: Small encrusting plant, to 2 mm in diameter, flat and smooth, margins entire and thin, conceptacles domed.

Habitat: Epiphytic on Cystoseira foeniculaceae in the lower littoral.

Distribution: British Isles, however probably under-recorded due to difficulty of identification. Europe: Mediterranean, Portugal, Atlantic coasts of Spain and France, Baltic Sea. Atlantic coast of North America:Canada, Massachusetts, Rhode Island, New Jersey, Virginia and Florida. Further afield: Jamaica, Canary Isles, Arabian Gulf, Red Sea, Kenya, South Africa, Indonesia and western Australia.

Similar Species: Few encrusting corallines can easily be determined with confidence. Microscopic examination often required.

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

iNaturalist: Hydrolithon farinosum at iNaturalist World Species Observations database.

WoRMS: Hydrolithon farinosum at World Register of Marine Species. Accepted name: Hydrolithon farinosum (J.V.Lamouroux) Penrose & Y.M.Chamberlain, 1993. AphiaID: 145118.

Classification: Biota; Plantae; Biliphyta; Rhodophyta; Eurhodophytina; Florideophyceae; Corallinophycidae; Corallinales; Hydrolithaceae; Hydrolithoideae; Hydrolithon