A foliose species with a deep copper to dark brown, smooth and often shiny thallus. The lobes often become much distorted and imbricate, the edges turning down and breaking up in small lobules with rhizines which may also grow from cracks in the surface. The under surface is black and rather granular with black, forked rhizines that form a dense, felt-like mass which protrudes beyond the edges of the lobes. Apothecia are very rare, and black.
Medulla: C+ red, K-
In Scotland, Umbilicaria polyrrhiza is common in central and northwestern Highlands where it is found on more or less nutrient-enriched, siliceous rocks and exposed boulders in upland sites. BLS distribution map
scottishlichens.co.uk 