Pileo 60–100 mm lato, hemispherico, dein plano-convexo, glutinoso, margine involuto, ochraceoluteo vel flavobrunneo interdum centro, ferrugineo maculato, cum KOH roseobrunneo. Lamellis emarginatis, pallide argillaceis, argillaceobrunneis, in statu senili. Stipite 80–140 mm longo, cylindrico, bulbo submarginato 30–50 mm lato. Velo universale albido. Velo partiale copioso, albido, cum KOH ope nullo. Carne albida. Sapore miti. Sporis 9–10 × 5–6 μm, limoniformibus, verrucosis, basidiis 24–30 × 6–8 μm, tetrasporigeris, fibulis praesentibus.
Type: USA. California: Mendocino County, Caspar, Caspar Cemetery, under Picea sitchensis, 22 Nov 2009, Bojantchev DBB25774 (Holotype UC 1860824; Genbank nrITS JF742659).
Etymology: from Greek: καλος = beautiful, μορφος = form, shape.
Straight to involute margin, uniformly ochre yellow (10YR 8/6–8/8), sometimes darker in older basidiomata (10YR 5/6–5/8) with a persistent lighter yellow zone near the margin (2.5Y 8/6) and rusty (5YR 6/6) spots where bruised; surface glutinous when wet, glabrous to dull glossy when dry, innately fibrillose, radially corrugated near the margin at age. Lamellae L = 70–110, crowded, 8–15 mm broad, pale clay (2.5Y 8/1–8/3) to grayish-white when young, never bluish, shading yellow brown to brown (7.5R 6/6–5/6) as the spores mature; edge even; attachment notched; lamellulae abundant. Stipe 80–140 mm long, 10–20 mm wide, cylindrical with a submarginate 30–50 mm wide bulb, white, without bluish tints, spotting brown where bruised. Universal Veil white, leaving volva-like remnants on the bulb. Cortina white, turning rusty brown due to mature spore drop, leaving an annular zone of dense fibrils on the stipe, occasionally forming a hairy appendiculate zone on the pileal margin. Context white, bruising brown. Odor weak, aromatic to none. Taste fungal, not unpleasant. Macrochemical Reactions 5% KOH carmine-red on pileus, uniformly pale yellow brown on context, strongest on mature basidiomata, negative on basal mycelium. UV non-fluorescent. Spore Deposit deep rusty brown.
Basidiospores (8.5–)9.0–10.0(–10.5) × (5.0–)5.2–5.8(–6.0) μm (mean 9.5 × 5.6 μm), Q = 1.54–1.77, Qav = 1.72 (N = 217, 11 basidiomata, seven collections), distinctly citriform, moderately verrucose. Basidia 24–30 × 6–8 μm, 4-spored, cylindro-clavate, clamped. Gill edge fertile or with clusters of elongated septate cells. Cystidia not observed. Pileipellis an ixocutis, duplex; epicutis medium thick, 6–14 layers of hyphae 2–7 μm diam., hyaline, hypodermium well developed, composed of interwoven to parallel cylindrical cells, 20–40 × 12–20 μm with refractive cytoplasmic pigment. Clamp connections common in all parts.
Habitat and distribution — Very common under Sitka spruce in Northern California, particularly in the Mendocino, Humboldt and Del Norte counties. We have never seen it south of Mendocino. Its distribution within the Sitka spruce range is apparently limited to northern California and southern Oregon (where we have collected it once). There are no matching records from Washington and British Columbia despite the intensive collecting and molecular cataloguing that has taken place in these regions. There are no other closely matching North American collections in the public sequence databases.