Cap: plano convex with a broad umbo, or conico-convex; 50 – 95 mm diameter; surface granulose to mealy and covered in small loose rounded scales which readily wash off in heavy rain; entire cap chalk white; margin entire or faintly striate.

Stipe: cylindrical with a more or less extended bulb at the base; 70 – 100 × 5 – 10 mm; glabrous and a yellowish straw colour above the ring, with white loose granules below; ring large, white, fragile; with prominent rhizomorphs at base often trapping substrate when the fungus is lifted.

Gills: free; white; relatively crowded and up to 5 mm deep.

Flesh: white, thin.

Smell: weakly of burnt rubber.

Spore print: white.

Spores: ellipsoid, 7.5 – 10 × 5.5 – 7 µm; with a germ pore and a distinct hyaline cap; stongly dextrinoid in Melzer’s reagent.

Notes: The all white granulose powdery cap, stipe with a ring, white granules and an elongated bulbous base are good field characters. Confirm by observing the germ pore and measuring spore size.

Patrick Leonard 2019