Umbilicaria freyi Codogno, Poelt & Puntillo

      Thallus formed of a single large lobe up to 8 cm in diameter, umbilical and fixed by its center, irregular margin more or less jagged, bordered by globular to irregular schizidia, upper surface gray, gray-brownish, paler to whitish in the center, underside finely grainy, light brown with sparse rhizines. Apothecia very rare, a little gyrous, black. Single spores, 8-11 x 6-8 µm. Photobiont: chlorococcoid. Cortex: C-, KC-, K-, P-, medulla; C + red, KC + red, K-, P-. Saxicolous, calcifuge, thermophilic species, coming on the vertical walls of rocks subjected to water flows.

N.B. A species very similar to Umbilicaria grisea and often confused, but the latter species is less thermophilic, has a darker underside and the edges of its lobes are devoid of schizidia.