Psoroma hypnorum (images of British lichens)

Thallus consisting of minute, green-grey to brown-grey squamules, green when wet (green-algal photobiont), accompanied by usually similar, inconspicuous, darker cephalopodia; apothecia usually abundant, about 3-4 mm in diameter, disks orange-brown, thalline margins whitish, convoluted and conspicuously nodular to squamulose, undersides pale, with patches of dense, minute, stiff hairs (but contrary to the impression from book descriptions, these hairs are not uniformly distributed and it may be necessary to check more than one apothecium). On soil, mossy trunks and in dune turf, predominantly in the north and west, very rare and coastal elsewhere.

Refs: Smith et al. (2009), 766; Purvis et al. (1992), 512; Dobson (2005), 373 (photo); Dobson (2011), 377 (photo); Jahns (1983), 234-5 (photo); Puntillo (1996), plate 34 (photo, in wet state); Moberg & Holmåson (1984), 168 (photo); Holien & Tønsberg (2008), 111 (photo); Nordic Lichen Flora (2007) 3: 110, 203 (photo); Hansen & Andersen (1995), 111 (photo); Brodo et al. (2001), 604-5 (photo); Øvstedal & Lewis Smith (2001), 292, plate 72 (photo); Lichen Atlas of the British Isles 3: 1205 (1998).

P. hypnorum is easily confused with Protopannaria_pezizoides, but the latter turns dark slate-blue to ± black when wet (contains a cyanobacterium as its photobiont) and the undersides of the apothecia lack patches of hairs. [Note, however, that the cephalopodia of P. hypnorum contain cyanobacteria, and a completely cyanobacterial morph has been reported in Scandinavia.]
Confusion is possible also with the disc-like squamules of Psora decipiens, which occurs in more calcareous situations.
Various non-lichenised, 'opeculate' discomycetes also grow amongst mosses on bare patches of soil, especially in dune turf, and could be confused with P. hypnorum, but generally they are brighter red, and they lack the squamulose thallus.

lastdragon.org

Images of British Lichens