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A thorough study of the type and several collections made by ourselves clearly showed that this species is taxonomically unrelated to Leucopaxillus. Details of its systematic position will be published in a later paper.

Holotype (K.): "Leucopaxillus urdesiacus Stev. and Taylor: on fallen log in Nothofagus forest: Butterfly Creek, Wellington, N.Z.: leg. Taylor (77), 8.1V.1961".—Herb. HK. ZT 67/239; "On branches of Phyllocladus alpinus (or Nothofagus fusca) in swampy forest; Kopara, Westland, N.Z.; leg. Horak, II.XII.1967". — Herb HK. ZT 67/269: "On mossy bark of Phyllocladus alpinus; N of Granite Creek near Ahaura, Westland, N.Z.: leg. Horak, 18.X11.1967". —Herb. HK ZT 68/179: "On rotten log of Phyllocladus alpinus; Lake Hochstetter. Westland, N.Z.: leg. Horak, 17.111. 1968".

Pileus 10-35 mm diam., convex later becomes flat or depressed. margin involute; dark grey or smoky dark brown; densely covered with minute squamules, sometimes pruinate, dry, neither hygrophanous nor striate. Lamellae adnate, emarginate or subdecurrent, crowded, when young white, later turning cream, brown coloured in old specimens or after bruising; gill edge fimbriate or floccose, con colorous. Stipe 5-30 x 2-7 mm. excentric or lateral, rarely centrally inserted, cylindrical. curved, solid; concolorous with pileus or paler, dotted with darker dots (caulocystidia) near the apex, fibrillose or squamulose towards the base, dry, veil remnants absent. Context white, below the cuticle and in the cortex of the stipe dark brown. Smell acidulous. Taste mild.
Spore print white. Spores 4.5-6(6.5) x 2-3 µm, elliptical or subcylindrical, sometimes curved and slightly comma-like, smooth, thin-walled, strongly amyloid, germ pore absent. Basidia 18-20 x 3.5-5 µm. Cheilocystidia 20-60 x 7-18 µm., clavate or cylindrical, occasionally with a short projection at the apex, hyaline, thin-walled, forming a sterile zone at the edge. Caulocystidia 30-65 x 6-7 µm, cylindrical, thin-walled, with brown membranal or epicellular pigment. Cuticle a palisade composed of erect or intermixed clavate or cylindrical cells (15-50 x 5-10 p.), membrane thick-walled, not gelatinised, strongly encrusted with brown pigment, clamp connections present.

On rotten wood and bark (infrequently on living trees) of Phyllocladus alpinus, rarely on Dacrydium cupressinum or Nothofagus spp. New Zealand.

Stevenson, Kew Bull. 19: 10, fig. 35. pl. 3, fig. 5. 1964.

Macroscopically the monotypic genus Pleurella resembles Melanoleuca Patouillard 1897 and to a lesser degree Leucopaxillus Boursier 1925. The existence of several distinct characters however, places Pleurella in an independent position between the two above-mentioned genera. The main differences separating Pleurella from Melanoleuca or Leucopaxillus are: smooth, strongly amyloid, elliptical or subcylindrical spores, conspicuous cheilocystidia, form of the carpophores and habitat.
This fungus normally grows on rotten wood of Phyllocladus alpinus (Podocarpaceae) but also occurs rarely on Dacrydium cupressinum (Podocarpaceae) or Nothofagus (Fagaceae). The species was observed many times in the wet lowland forests of the West Coast of the South Island, between Reefton and Haast.

[Notes from Kew Type specimen, PRJ 2010] Kew images.

Pleurella ardesiaca is a lignicolous species from New Zealand characterized by smooth, amyloid spores and presence of cheilocystidia and clamp connections, which suggest a close relationship with Porpoloma s.st r. ( Horak, 1971). However, the lignicolous habitat is not consistent with placement in Dennisiomyces or Porpoloma. An ITS sequence (JQ694106) is publically available from a collection (PDD 87446) referred to as Pleurella ardesiaca from New Zealand. BLASTn results suggest the nearest alliance of this specimen to Baeospora in the Marasmioid clade (Matheny & al., 2006) or to Hypsizygus (Gillet) Singer in the Lyophyllaceae. A thorough analysis of the type is required to conf irm its taxonomic and phylogenetic position.

Pileus 2-3 cm diam., dark grey, convex with strongly down-rolled margin, silky fibrillose; flesh white, solid, with a water soaked layer above the gills. Gills adnexed, pale grey, long and short intercalating, some forking. Stipe 2.5 x 0.5-0.7 cm, solid, fleshy, pale grey fawn with darker grey markings, base surrounded by grey hyphae. Spores 5-6 x 2-5-3 µm, strongly amyloid (Fig. 35); print white.

On fallen log in Nothofagus forest, Butterfly, Wellington, 8.4.1961, G. M. Taylor (type).

Pileus 2-5 cm diam., fusco-griseus, convexus, margine valde deorsum revoluto, sericeo-fibrillosus; came alba solida, strato aquoso supra lamellas sito. Lamellae adnexae, pallide griseae, longiores cum brevioribus intercalatae, nonnullae furcatae. Stipes 2.5 x 0.5-0.7 cm, solidus, carnosus, pallide griseo-hinnuleus, fuscius griseo-notatus, basi hyphis griseis circumdatus. Sporae 3-6 x 2.5-3 µm, valde amyloideae, in cumulo albae.

Typus: G. M. Taylor 77.