Peltigera rufescens (Weiss) Humb.
Common on dry, basic soils and dunes. The white-tomentose lower surface, with branched, confluently-based rhizines that are white near the thallus margins but conspicuously dark-brown further under the lobes, veins also becoming dark brown under the lobe-bases helps separate this species from similar lichens such as P.membranacea
Smith et al. editors (2009) The Lichens of Great Britain and Ireland
Dobson (2018) Lichens: an Illustrated Guide to the British and Irish Species
Ahlti et al. editors (2012) Noric Lichen Flora. Volume 3: Cyanolichens