Description: An encrusting coralline alga growing to over 2 cms in diameter and 1 mm thick but with a thin margin. Smooth but may become very knobbly, up to 5 mm high. Margin without orbital ridges.

Habitat: Common. Epilithic in mid to upper littoral, not found in the sublittoral.

Distribution: British Isles including the Shetlands. Europe: the Mediterranean, the Adriatic and Norway. Further afield: Morocco.

Similar Species: Lithophyllum incrustans and can be difficult to distinguish on the shore. L. incrustans has a thick margin and overgrows L. orbiculatum.

Key Identification Features:

• Smooth becoming knobbly, without orbital ridges.

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

iNaturalist: Lithophyllum orbiculatum at iNaturalist World Species Observations database.

WoRMS: Lithophyllum orbiculatum at World Register of Marine Species.