Lecanographaceae Alyxoria mougeotii (Opegrapha mougeotii) Growth type crustose Chemical results negative. BLS conservation evaluation: LC NS On steep, sheltered limestone, mortared walls and calcareous sandstone Thin, often immersed thallus with scattered or contiguous lirellae, the discs soon widely exposed with yellow-green or grey-blue pruina. Spores 5-7(-8) septate, (20-)25-33(-55) × 5-8(-10) µm. Micro photo below. Similar: Opegrapha lithyrga (siliceous rocks, 5-7 septate spores, 20-35 x 2.5-5 µm, with gelatinous perispore 1-1.5 µm thick), Opegrapha calcarea (3-septate spores) and O. areniseda (spores usually 3-5 septate)

Microscope photograph

Opegrapha mougeotii
Kimmeridge and Portland, Dorset. February 2014 and 2016