Description: Know from south Kerry, Dublin and west Donegal, this species is lichenicolous on the thallus of Xanthoria parietina over which it can grow singly or in groups. It is similar to O. rupestris, but that species grows on crustose Verrucaria spp. on hard limestones. The three-septate spores are 12–17µm long.

Key Identification Features:

• A lichenicolous lichen of Xanthoria spp.
• Discs slit-like, spores three-septate and 12–17µm long.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Phacothecium varium at iNaturalist World Species Observations database.