Thallus: Foliose, composed of irregular flattened, overlapping branches which are only loosely attached to the bark; the branches are 1-4 mm (.04-.15 in) wide and comparatively thick and hollow; upper surface smooth, dull pale gray to greenish-gray when dry; similarly colored when wet; lower surface black or very dark brown, often wrinkled, lacking rhizines. 

Apothecia: Rare.

Soredia: Common; formed on the underside of the tips of branches;  when they protrude from underneath, they appear as crescent-shaped masses (Fig. A).

Isidia: Lacking.

Comments: See comments under Hypogymnia
tubulosa.