Description: Encrusting thallus up to 12 cms and up to 2 mm thick becoming knobbly or simply branched, irregular. Margin without orbital ridges and a smooth surface. Also to be found as unattached plants growing into unattached masses irregularly branched. Conceptacles crowded and slightly domed with a rim surrounding the central pore plate.

Habitat: Very Rare. Epilithic in the littoral.

Distribution: British Isles: Northumberland and Orkney. Atlantic coast of North America: Canada.

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

iNaturalist: Lithothamnion lemoineae at iNaturalist World Species Observations database.

WoRMS: Lithothamnion lemoineae at World Register of Marine Species.