Description: This inconspicuous lichen grows mostly on the leaves and stems of mat-forming mosses such as Hypnum cupressiforme agg., and willow bark. It looks very like A. muscigena (described elsewhere) and will apparently grow with it, but is distinguished by the three-septate spores and paraphyses with capitate apices. In Ireland, the species is known from the County Antrim coast.

Key Identification Features:

• Very like A. mucigena but spores three-septate
• On slightly bleached leaves of mat-forming mosses and on willow bark.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Arthonia mediella at iNaturalist World Species Observations database.