How to tell Egghead mottlegill from Garland roundhead

The cap is 2 to 6 cm across, sometimes up to 9 cm. It's egg-shaped when young, then like half an egg or a blunt cone, only rarely convex. The margin isn't lined; it overhangs the gills and sometimes carries scraps of veil.

It's whitish, cream or pale clay-coloured, darker in the centre, and fades with age. When wet it's sticky; when dry it's smooth and shiny, often wrinkled or cracked.

The cap is small, 2 to 5 cm across and only rarely up to 8 cm. It starts out hemispherical, becomes convex and finally almost flat, and in old specimens the margin may turn upwards.

The colour is lemon yellow, golden or ochre, a little darker in the centre, and it fades to pale yellow with age and sun. The surface is smooth and slightly sticky or greasy in wet weather, but it dries quickly, and old or dried-out caps can become finely scaly. Young caps often have white scraps of veil hanging from the margin.

The gills are attached, crowded and broad. They start off whitish or greyish, become mottled with black patches and end up black, with whitish edges.

The spore print is black.

The gills are attached to the stem and crowded, with many shorter gills in between. They begin pale lilac-grey, turn purplish grey and end up dark purple-brown to almost black. The gill edges are paler and look slightly fluffy. The gills are the quickest way to rule out an Agaricus: field mushrooms have free gills that are pink when young.

The spore print is dark purple-brown to blackish. The spores are smooth and ellipsoid, roughly 7–10 × 4–5.5 µm.

The stem is 6 to 15 cm tall and 3 to 10 mm thick, long and slender compared with the cap, whitish or cap-coloured, paler and finely powdery at the top, slightly swollen at the base, brittle and hollow.

Above the middle there's a thin white ring that turns black on top from spores. It's fragile and can fall off, so look for it on young specimens.

The stem is short and sturdy, 2 to 6 cm tall and 4 to 10 mm thick. It is white, sometimes yellowing with age, smooth or faintly fibrous, solid at first and later hollow. White strands of mycelium are often visible at the base.

The ring is the key feature. It is membranous, white and sits on the upper half of the stem, and it stays put as the mushroom ages. Its upper side is finely grooved, and as the cap matures the falling spores settle on it and darken it to purple-brown. There is no volva at the base.

The flesh is thin, soft and whitish, pale yellowish and brittle in the stem, and doesn't change colour when cut.

The flesh is white and firm, thick in the centre of the cap and thinner towards the edge. It doesn't change colour when cut or broken. The taste is mild, not bitter.

The smell is indistinct.

The smell is faint and slightly radishy, and sometimes barely there at all. Field guides don't describe a mealy smell for this species: that belongs to its dung-loving relative, the dung roundhead. So smell won't identify it; check the gills and the ring instead.