Toadskin lichen is aptly named. It is found on boulders and cliff faces: sandstones, granites, rhyolites, other acid rocks; and very dry surfaces. It is found throughout much of North America.
Identification: This is an umbilicate lichen, attached
to a rock at a single point. Each lichen is up to 3½″ (9 cm) in diameter, with pustules
(bumps) that appear to radiate from the center. The upper surface is gray, flecked with black apothecia;
or may be brown with
rust-colored bumps. A technical description is available at the Consortium of North American Lichen Herbaria.
11/8/2009 · Yellow Trail from Pearl Hill State Park to Willard Brook State Park, Ashby, Massachusetts · ≈ 11 × 7″ (27 × 18 cm) ID is uncertain