Description: Now extinct in Ireland this is a species faithful to poplar trees. The white, K+ faint yellow thallus forms small wheel-like patches with scattered flat black, non-pruinose discs. The spores (12–14 x 4–5) are one-septate, hymenium K+ violet.

Key Identification Features:

• Thallus forming round patches, snow white K+ faint yellow; discs black
• Spores one-septate, hymenium with coloured pigments, K+ violet.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Arthonia galactites at iNaturalist World Species Observations database.