Lathagrium cristatum  

Thallus 2-5(-10) cm, foliose, rounded, semi-circular, or irregular, often dying away in the centre when old, deeply lobed. Lobes to 3 mm wide, rather thin, narrow, radiating, notably concave, irregularly branched, contiguous or discrete; lobe margins elevated, wavy, ± entire or ± incised, distinctively dentate to sinuously lobulate, not swollen. Upper surface dark olive-green-brown to black; lower surface with rounded hapters forming large white tufts.
Anamorph: no information available.
Teleomorph: ascomata apothecia, often densely crowded, sometimes absent, ± marginal, sessile or stalked. Disc to 5 mm diam., flat, with an even thalline margin. Asci 4- to 6- (to 8-) spored. Ascospores 18-32 × 8-13 μm, ellipsoidal, with ± acute ends, submuriform.