Parmotrema perlatum (Huds.) M. Choisy
A foliose species with smooth pearl-grey to greenish lobes with delimited mardinal and apical soralia. Very short, inconspicuous and often sparse, black, marginal cilia. The black underside has simple rhizines and a bare, tan-coloured zone towards the margin. A species heavily biased towards the south and west becoming scarce in the north-east. Found on rocks and trees.
Smith et al. editors (2009) The Lichens of Great Britain and Ireland
Dobson (2018) Lichens: an Illustrated Guide to the British and Irish Species
Thell & Moberg, editors (2011) Nordic Lichen Flora, Volume 4: Parmeliaceae