Cortinarius ursus is a striking, dark, heavily squamulose species of Nothofagus forest, notable for its coarse, hirsute, concentric cap scales, deep violet lamellae, and persistent purplish membranous veil forming a fixed collar. It is gregarious but uncommon in New Zealand’s southern beech forests.

Pileus: 35-70 mm, dry, non‑hygrophanous. Shape rounded with flattened apex, later convex. Surface covered in large, hirsute, concentric squamules (1-1.5 mm high), dark umber to black‑brown, often purplish when young. Ground colour paler brown; margin concolorous, indistinctly striate.
Lamellae: Deep saturated violet when young. Moderately crowded (L = 48, l = 3). Adnate to narrowly emarginate. Edge concolorous, sometimes slightly crenulate.
Stipe: 45-9 x 1-16 mm, cylindrical or tapering downward. Pale rosy to grey‑violet, soon purplish brown. Covered in fibrillose, brown‑violet to blackish veil remnants. Ends in a persistent, erect, membranous collar, apex violet.
Veil: Membranous, tenacious, abundant, brown‑purple.
Context: Whitish‑grey, sometimes yellowish in the stipe base.
Odour/taste: Iindistinct.