In moss under Juniperus communis. Autumn. Only known from the type locality.

Pileus 5-17 mm across, conical, parabolical to convex, with or without a small umbo, sulcate, translucent-striate, prominently white-pruinose, glabrescent, grey-brown or dark grey, turning paler grey, mostly with a pale brown centre. Lamellae 15-17 reaching the stipe, ascending, narrowly adnate, at times decurrent with a short tooth, with age veined and anastomosing, dorsally intervenose, grey to dark grey, sometimes blackish grey. Stipe up to 70 x 2 mm, hollow, straight, terete, equal, densely puberulous, glabrescent, brownish or grey brown, apex whitish or pale grey, the base fairly dark brown, with age turning grey-brown to silvery grey, the base densely covered with long, coarse, flexuous, whitish fibrils. Odour nitrous.

Basidia 24-30 x 6-8 µm, clavate, 4-spored, with sterigmata up to 9 µm long. Spores 7-11 x 4-5.5 µm, Q = 1.5–2.2, Qav = 1.8, pip-shaped, amyloid. Cheilocystidia 28-47 x 8-18 µm, forming a sterile band, clavate, fusiform, lageniform. Pleurocystidia similar. Lamellar trama dextrinoid. Hyphae of the pileipellis 2-5 µm wide, covered with simple to branched, flexuous or curved, cylindrical excrescences 2-18 x 1-2.5 µm, forming dense masses and tending to become somewhat gelatinized. Hyphae of the cortical layer of the stipe 2-4 µm wide, smooth but occasionally covered with short excrescences near the terminal cells, producing numerous, simple to rarely forked, flexuous to fairly straight or curved, cylindrical, thin-walled, hair-shaped caulocystidia, often somewhat widened at the base 25-180 x 1.5-3 µm. Near the apex of the stipe the caulocystidia are more cystidia-shaped, clavate or with an inflated base and a short neck, smooth or with a few coarse excrescences. Clamp connections observed at the base of the basidia and the cheilocystidia and at the septa of the hyphae of the stipitipellis.

This taxon was initially mistaken for Mycena leptocephala (Pers.) Gillet. The microscopic details, however, are so special that it can be told apart from any other Mycena. In section Fragilipedes, so far, there are five species known with long, "hair-shaped", elements sprouting from the hyphae of the stipe cortex: Mycena pilosella Maas Geest., M. pruinatipes Robich, M. scirpicola M. Villarreal, Heykoop, Esteve-Rav. & Maas Geest., M. spinulosipes Robich, and M. villicaulis Maas Geest. Neither of them matches the present taxon (Aronsen 2009).

Collections examined:

VESTFOLD: Tjøme, Moutmarka 29 Sept. 1998, leg. A. Aronsen A 02/98; Tjøme, Hvasser, Sønstegård 22 Oct. 2006, leg. A. Aronsen A 16/06; 11 Oct. 2008, leg A. Aronsen A 83/08.