ASCOMYCOTA | ARTHONIOMYCETES > ARTHONIALES > Arthoniaceae

Genus Arthonia, meaning 'to sprinkle' referring to the scattered apothecia

Common name:            -

Synonym:                     Opegrapha calcarea

Habitat: Coastal

Substrata:                     Rock

Growth form:                Saxicolous

Thallus:                 Crustose

Apothecia:                    Lirellate

BLS identity rating:        Graded 1/5 (identification should be relatively straightforward)

Thallus variable according to substrata, immersed or thinly cracked, white, buff, grey-pink, pink or green-pink; lirellae are black, short to about 1mm long, simple, joined, very often branched, radiating or star-shaped, scattered or heaped together, often forming roughly circular or more irregular patterns.

Whilst this particular species occurs mainly on shaded limestone rocks on or near the coast, the described form also encompasses several morphotypes, notably Opegrapha conferta and Opegrapha chevallieri, which are more likely to be found on either coastal or inland basic or siliceous rocks in the case of the former, or man-made structures for the latter.