New Zealand: "Westcoast, Lake Haupiri, Kopara; 8.xii.1967, leg. Horak" (PDD, 27118: holotype; ZT, 67/222; isotype). "Canterbury, Mt Grey, Kowai River; 31.xii.1968, leg. Horak" (ZT, 68/692).

Pileus -50 mm diam., convex with broad umbo, campanulate, expanded in old carpophores; colour varying from beige, light brown to hazel-brown, yellow or ochre tints absent; strongly innate fibrillose, rimose and splitting towards the striate margin, centre smooth; subviscid when wet, veil remnants absent. Lamellae adnexed to adnate, crowded (1 -7), ventricose; whitish grey turning grey-beige, with white fimbriate edges. Stipe 35-60 x 4-6 mm, cylindrical, with strongly marginate bulb (-14mm diam.); white later turning light brown with reddish or pink tints; pruinate all over, often substriate with longitudinal lines; veil remnants none, dry, solid, single or in groups. Context white in pileus, reddish brown in cortex of stipe. Odour not distinctive.
Spores 9-11 x 6.5-9 µm, nodulose, knobs conspicuous, brown. Basidia 25-40 x 10-13 µm, 4-spored. Cheilo- and pleurocystidia 45-90 x 10-24 µm, fusoid, thick-walled (-4 µm diam.), encrusted, hyaline. Caulocystidia identical. Cuticle a cutis of repent cylindrical hyphae (6-15 µm diam.), encrusted with yellow-brown pigment. Clamp connections present.

On soil in Nothofagus forests (N. cliffortioides, N. menziesii, N. fusca). New Zealand.

Pileo -50mm lato, convexo-campanulato, argillaceo vel avellano, fibrilloso-rimoso, subviscido. Lamellis adnexis, albogriseis dein argillaceis, albofimbriatis. Stipite -60 x -6 mm, cylindraceo, bulboso, albo rufescente, pruinoso. Odore nullo. Sporis 9-11 X 6.5-9 µm, gibbosis. Cheilo et pleurocystidiis fusoideis, crasse tunicatis, incrustatis. Habitatio in silvis nothofagineis. Nova Zeiandia. Typus (PDD, 27118).

Macroscopically there are no differences between A. avellana from New Zealand and Inocybe fuscata Singer from the Nothofagus forests of Chile and Argentina. Microscopical examination, however, shows that the morphology of the spores and cystidia is distinct. Inocybe tequendamae Singer (from Colombia) is another closely related species in South America associated with Quercus spp.