Panaeolus papilionaceus is a small, coprophilous, black-spored mushroom recognised by its bell-shaped cap, mottled gills, and the distinctive white, tooth-like veil fragments that hang from the margin. It is inedible and non-psychoactive.

Cap: 10-30 mm across; obtusely conical to bell-shaped with age. Whitish, grey, brownish, or reddish-brown; may develop fine cracks or raised ridges. Dry, smooth to silky; sometimes finely hairy in age. Margin often adorned with white, tooth-like veil remnants (“petticoat”).
Gills: Attached or pulling away from the stem with age. Close to crowded. Start greyish, then develop black mottling, eventually black overall; edges remain whitish.
Stipe: 40-100 mm x up to 5 mm, slender, brittle. Finely hairy, coloured like the cap but paler at the apex, darkening or reddening toward the base. No ring.
Flesh: Very thin and insubstantial.