Helvella acetabulum  

Anamorph: not known.
Teleomorph: ascomata apothecia, 1.5-7 cm broad, at first regularly cupulate, when adult expanded and irregular, hymenium brownish to dark brown, sometimes with a violet tinge, outside pubescent, above greyish brown to brown, below gradually becoming pale brownish to nearly whitish-cream, with prominent whitish to cream, angular to sharp-edged branching ribs, which may reach the margin; stipe mostly well-developed, inside chambered, 2-6 cm high, not clearly distinct from the gradually widening apothecium. Paraphyses 4-6 µm diam., slightly enlarged above, walls ± brownish. Asci 16-21 µm broad, cylindrical, the apex rounded, 8-spored. Ascospores 16-18 (-19) x 11-12 µm, broadly ellipsoidal.

Description mostly adapted from Dissing (1966).