Description: A small flat encrusting coralline with a diameter of up to 5 mm without orbital ridges. Conceptacles slightly raised or slightly sunken, more or less flush with thallus. Overgrown by most other corallines.

Habitat: Very rare. Epilithic in the lower littoral.

Distribution: British Isles: Norfolk and Co. Clare, probably more widely distributed. Europe: Spain and France. Further afield: Canary Islands, South and East Africa, India, Mexico, Samoa, Tahiti and Japan.

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

iNaturalist: Hydrolithon samoense at iNaturalist World Species Observations database.

WoRMS: Hydrolithon samoense at World Register of Marine Species. Accepted name: Harveylithon samoënse (Foslie) A.Rösler, Perfectti, V.Peña & J.C.Braga, 2016. AphiaID: 1041650.

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