Pileus -35 mm diam., convex to umbonate-expanded or campanulate; pale brown, brown or fuscous, often with greenish or olive tinge; dry, densely covered all over with coarse, squarrose scales and squamules; margin estriate, veil remnants absent. Lamellae adnexed to adnate, ventricose, crowded; pale beige-ochraceous or beige-yellow, turning argillaceous or brown, reddening after bruising, edge albo-fimbriate. Stipe -65 x -5 mm, cylindrical, equal; concolorous with pileus or paler, black-green at base, covered with concolorous scales and squamules; dry, becoming hollow, single and cespitose. Context brown, reddening after exposure, black-green at base. Odour and taste fruity. Chemical reactions on pileus: KOH negative.
Spores 8.5-11 x 5-6.5 µm, ovoid to subreniform, brown, smooth. Basidia 28-38 x 7-9 µm, 4-spored. Cheilocystidia 15-40 x 7-12 µm clavate to subcylindrical, hyaline, thin-walled, forming sterile edge. Pleurocystidia absent. Cuticle a trichoderm of cylindrical not gelatinised hyphae (5-12 µm diam) entrusted with brown pigment. Clamp connections present.

New Zealand: “West coast, Araua, Granite Creek: 17.xii.1967 leg. Horak (PDD, 27121: holotype; ZT. 67/262: isotype)”. "Nelson, Tophouse Saddle; 4.iii.1968; leg. Horak (ZT, 68/108)."

On soil under Nothofagus (N. fusca, N. cliffortioides), also among Sphagnum, New Zealand.

Pileo -35 mm lato, e convexo campanulato, brunneo-fusco coloribus olivaceis tinctu, squamato-squarroso. Lamellis adnexis, ochraceo-alutaceis dein argillaceis, rubescentibus. Stipite -65 x -5 mm, cylindraceo, apicaliter lanoso, basim versus squamoso-squarroso, pileo concolori, ad basim intense nigro-viride, sicco. Odore grato. Sporis 8.5-11 x 5-6.5 µm, ovoideis vel subreniformibus. Cheilocystidiis cylindraceo-clavatis, numerosis, tenuitunicatis, fibulatis. Habitatio ad terram in silvis nothofagineis. Nova Zeiandia. Typus (PDD, 27121).

The most distinctive macroscopic character of this species is the green-black context at the base of the stipe. As the specific epithet of the New Zealand fungus indicates, this taxon is closely related to I. calamistrata (Fr.) Quel. which, however, differs by having larger spores cheilocystidia.