Description: This is a species of upland ridges, crags and boulders that you would only find with careful searching. The rather small, warted thallus (sometimes C+ red) forms a cracked-mirror-like crust, the pieces of which surround the spherical discs (perithecia). The eye picks it up as a mosaic smear of yellow-brown or sometimes as a vivid green. Under the microscope, the muriform spores are broadly ellipsoid. In Ireland, it was most recently recorded from Counties Mayo and Tyrone.

Key Identification Features:

• Thallus cracked, warted (C+ red), yellow-brown to vivid green
• Discs = perithecia, spores muriform, broadly ellipsoidal; damp boulders, siliceous rocks by water: uplands.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Protothelenella corrosa at iNaturalist World Species Observations database.