Description: Encrusting flat alga, completely and firmly attached to the substrate, relatively thin with clear orbital ridges. Up to 8 cms in diameter usually with a mosaic of low mounds of conceptacles raised and closely packed, later when the tops are lost giving a cratered appearance except at the edge. Conceptacles not becoming buried.

Habitat: The most common coralline growing epilithically and epizoically. Littoral and sublittoral to 30 m deep.

Distribution: Throughout the British Isles including the Shetlands. Europe: Mediterranean, Azoresw, Portugal, Atlantic coasts of Spain and France, Netherlands, Baltic Sea, Norway, Faroes and Iceland. Greenland. Atlantic coast North America: Canada, Maine, New Hampshire and Massachusetts. Further afield: Arctic Sea, Canary Isles, California, Mexico, Japan, Russia, Mauritius and South America.

Key Identification Features:

• A mosaic of low conceptacles, or craters. Clear orbital ridges at the edge. Overgrown by most other encrusting coralline algae.

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

iNaturalist: Phymatolithon lenormandii at iNaturalist World Species Observations database.

WoRMS: Phymatolithon lenormandii at World Register of Marine Species. Accepted name: Phymatolithon lenormandii (J.E.Areschoug) W.H.Adey, 1966. AphiaID: 145202.

Classification: Biota; Plantae; Biliphyta; Rhodophyta; Eurhodophytina; Florideophyceae; Corallinophycidae; Hapalidiales; Hapalidiaceae; Phymatolithon