''Calicium quercinum'' is a species of

lichen A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.Caliciaceae. It is native to Europe and Northern America.

References

quercinum Lichen species Lichens described in 1797 Lichens of Europe Lichens of North America Taxa named by Christiaan Hendrik Persoon {{Caliciales-stub