Description: This crustose lichen grows on shaded siliceous rocks often in association with Opegrapha gyrocarpa. The brown thallus is only evident around the discs which are rounded in shape or slightly slit-like. Spores one-septate (average length equals 11-14&

371;m), colourless, becoming browner with age. In Ireland, the species is restricted to County Down.

Key Identification Features:

• Thallus brown to greenish usually intermingling with similarly coloured thalli on shaded acid rocks; discs round to lirellate with one-septate spores
• Associated with lichens of siliceous underhang communities.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Arthonia granitophila at iNaturalist World Species Observations database.