Arthonia anglica

Arthonia anglica is a species of lichen-forming fungus in the family Arthoniaceae. The lichen forms grey-white to pale fawn patches on tree bark, bounded by a dark brown line, and is mostly embedded within the outer bark layer. Its reproductive structures are numerous star-shaped to irregularly star-shaped features that are pale to dark reddish-brown and can reach up to 12 mm across in the largest groupings. The species occurs on mature hardwood trees in long-established woodlands, recorded from beech and holly in Britain, and from various hardwoods including maple and hornbeam in eastern North America....read more on Wikipedia.