Caloplaca subpallida H. Magn.
Caloplaca arenaria auct. p.p. (Pers.) Mûll. Arg.
Thallus crustose very thin and even sometimes absent or hardly visible, dirty gray, brownish-gray. Apothecia numerous, small, 0.2-0.6 mm in diameter, flat disc, orange-red becoming a little brownish with age, margin clear and well developed, paler. Elliptical polarilocular spores, colorless, 13-17 x 4-6 µm with equatorial thickening of 3-5 µm according to the literature, 11-17 x 4-7 µm with equatorial thickening of 3-5 µm according to our measurements. Photobiont; green algae. Thallus; C-, K-; apothecia: C-, K + purple. Saxicolous species coming on the vertical faces of the rocks for the sun and rain, parasitic on crustose lichens: Aspicilia, Rhizocarpon, Acarospora, etc., probably frequent but not very visible on the ground. N.B. This species belongs to the group of Caloplaca arenaria to which it closely resembles. Caloplaca arenaria differs (sometimes with difficulty) by more red coloration and smaller spores but some British authors do not separate the two taxa.