Description: This species grows on the thallus of Amygdalaria pelobotryon (which grows on base-rich siliceous rocks in lake ‘splash zones’ or near streams and rivers) and is only known from County Antrim in Ireland. The small, black rounded discs produce one-septate spores with a ‘halo’-like surround.

Key Identification Features:

• Lichenicolous on the thallus of Amygdalaria pelobotryon
• Discs tiny, black; spores one-septate with transparent halo-like outer coat.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Arthonia almquistii at iNaturalist World Species Observations database.