Umbilicaria torrefacta (Lightf.) Schrad.

    Umbilicated foliose thallus generally formed of a single lobe 6-8 cm in diameter, fairly thick, margin incised, undulating, often perforated, upper surface smooth to slightly rhymed, cracked or granular, in older thalli it is often "snakeskin" and pseudosquamose, brown, pale brown, if dry, olive-brown if wet; lower surface with filiform trabeculae and rare simple rhizomorphs, light brown darker in the center (appearance of a cut in a spongy bone). Apothecia fairly frequent, circular, gyrous ("licorice roll"), semi-immersed in the thallus and very little in relief, black. Ascospores simple, hyaline, elliptic, 7-12 x 5-7 µm. Photobiont: chlorococoid. Medulla: K- or K+/- yellow, C+ red, KC+ red, P- or P+/- orange. Not a rare, mountainous, saxicolous species found on damp siliceous rocks.