Description: This small, foliose lichen with a circular thallus only 1cm wide stands a good chance of being overlooked as it blends so well on brick and stone and tree bark. Unlike its relative, P. orbicularis (described elsewhere), the thallus of this species is often ragged, so that on vertical brick, the lobes can hang loose. The dry, grey-brown lobes support marginal isidia along their narrow edges which can dissolve effortlessly after a short time, into soredia. The white or pale brown underside easily separates it from small forms of P. orbicularis whose undersurface is blacker. Discs are unknown in Ireland. Calcareous stonework and brick; widely scattered in counties north of the Shannon Estuary.

Key Identification Features:

• About 1cm diam. brown, circular thalli with pale pink or white undersides
• Narrow lobes edged freely with isidia giving a jagged appearance.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Phaeophyscia nigricans at iNaturalist World Species Observations database.