New Zealand: "Westcoast, S of Lake Hochstetter: 17.iii.1968, leg. Horak (PDD, 27131: holotype: ZT, 68/175: isotype)". "Nelson, Puponga; 17.v.1968, leg. Horak (ZT, 68/476)." "Fjordland, East slopes of Mt Luxmore; 26.iii.1969, leg. Horak (ZT, 69/181)." "Fjordland, East slopes of Mt Luxmore; 9.iv.1969, leg. Horak (ZT, 69/326)."

Pileus 8-25 mm diam., hemispherical when young, becoming convex or conico-convex to campanulate; brown, fuscous, umber-brown; in young carpophores margin densely covered with silvery, sub persistent conspicuous, fibrillose remnants of the veil; squamulose to scaly at disc, rimose or fibrillose towards margin, dry, estriate. Lamellae adnexed, ventricose, crowded (L -20, 1 -3), argillaceous when young soon turning deep brown or umber-brown, edge albofimbriate. Stipe 20-50 x 1-2 mm, cylindrical, equal; concolorous with pileus, often with red-brown or chestnut-brown tinge; pruinose all over, at base with white fibrillose or woolly, appressed veil remnants, which disappear with age; dry, slender, hollow, single and cespitose. Context dark brown. Odour and taste not distinctive. Chemical reactions on pileus: KOH-negative.
Spores 6.5-8.5(9) x 4-5 µm, amygdaliform brown, smooth. Basidia 20-26 x 5-7 µm 4-spored. Cheilo- and pleurocystidia 40-60 x 12-18 µm, fusoid to lageniform, metuloid (-3 µm diam.), hyaline to yellowish, encrusted with crystals. Caulocystidia -130 x -20 µm, elongate-fusoid, metuloid, crystals present. Cuticle a trichoderm of cylindrical hyphae (5-10 nm diam.), encrusted with brown (KOH) pigment; hyphae of veil 2-4 µm diam.; clamp connections on septae.

On soil among moss and litter under Nothofagus (N. cliffortioides, N. menziesii) and Leptospermum (L. scoparium, L. ericoides), rarely also on rotten wood of Nothofagus. New Zealand.

Pileo -25 mm lato, convexo, convexo-conico vel campanulato, fusco vel umbrino, ad marginem fibrillis albis e velo instructo, squamuloso marginem versus rimoso-fibrilloso, sicco. Lamellis adnexis, pileo concoloribus vel pallidioribus. Stipite -50 x -2 mm, cylindrico, pileo concolori vel castaneo-brunneo, pruinoso, lanuginoso-fibrilloso ad basim. Odore nullo. Sporis 6.5-8.5(9) x 4-5 µm, amygdaliformibus, brunneis. Cystidiis fusoideis, metuloideis, incrustatis. Habitatio ad terram (vel rarissime ad lignum putridum) sub Nothofago Leptospermoque. Nova Zeiandia. Typus (PDD, 27131).

Inocybe umbrosa is distinguished by dark brown to fuscous colours of the carpophores. The slender stipe is pruinose all over and the rather small (-50 x -15 µm) fusoid cheilocystidia are intermixed with clavate thin-walled cystidia without crystals.