Summary:
Distinctive characters of Calocybe onychina in the genus Calocybe are purple-red to wine red cap, bright yellow gills and purplish to pink stem. Rugosomyces onychinus (Fr.) Raithelh. was the current name in the online Species Fungorum, accessed March 24, 2014, but Rugosomyces is synonymized with Calocybe in the Tenth Edition of Dictionary of the Fungi

Cap:
2-9cm across, broadly convex to obscurely umbonate, nearly flat when old, margin inrolled when young; purple-red to wine red when young, with darker shades of purple-red when old; bald, margin often crenulate [finely scalloped] when old, (Bessette), 3-6(8)cm across, flat-convex becoming flat, the margin at times uplifted; evenly colored deep vinaceous red to purple-red, not fading appreciably in drying; bald, dull and dry in appearance but at times +/- shiny when old, cuticle remaining continuous, (Mitchel)

Flesh:
firm; white to pale yellow, (Bessette), brittle soft; watery gray fading to pallid; in stem watery vinaceous buff, (Mitchel)

Gills:
adnate, close, medium broad, one tier of subgills; dull deep yellow, (Bessette), adnate to slightly decurrent; crowded, close, narrow; pale ocher yellow and color persisting when old, not spotting where injured, (Mitchel)

Stem:
2-4.5cm x 0.4-1.5cm, widening somewhat toward base; "dull white with a pinkish to purplish hue especially over the upper half"; dry, canescent [hoary], (Bessette), 2-5cm x 0.8-1.5cm at top, equal to clavate [club-shaped], fragile; a paler vinaceous color than cap, pallid at base; dull to unpolished, (Mitchel)

Odor:
farinaceous, even somewhat cucumber-like, (Bessette), not distinctive (Mitchel)

Taste:
mild (Bessette), mild or farinaceous (Mitchel)

Microscopic spores:
spores 3-4 x 2-3.5 microns, nearly round to short elliptic, inamyloid, thin-walled; basidia 4-spored, 24-30 x 5-8 microns, clavate, thin-walled, with siderophilous granulations in carmine-acetic acid; cystidia absent; cap cuticle a loosely arranged hymenoderm of erect pileocystidia 20-34 x 2.7-7.8 microns, hypha-like to clavate or sometimes tenpin-shaped, thin-walled, colorless; clamp connections absent, (Bessette), spores 3-3.5 x 2 microns, elliptic, inamyloid; basidia 4-spored, 18-20 x 3-4 microns; pleurocystidia and cheilocystidia not found; cap cuticle a compact cellular layer of trichodermal origin, the units 2-3(4) cells long, the terminal cells forming an indistinct palisade, pigment dissolved in cell sap; clamp connections present, (Mitchel)

Spore deposit:
white (Bessette, Mitchel)

Notes:
It is rare in the central Rocky Mountains of ID (Bessette). It has been found in WA (Lorelei Norvell, pers. comm.), CA (Desjardin), and CO (Mitchel). It was reported by A.H. Smith from OR (Mitchel), and by Oluna Ceska in December from BC. According to Mitchel(1) it was reported by Barrows from NM.

EDIBILITY

edible at least in Europe

Synonyms and Alternate Names:
Tricholoma onychina Fr.