How to tell Yellow swamp brittlegill from Jewelled amanita

The cap is 5-10 cm across, convex with an inrolled margin when young, becoming flattened with a slightly depressed centre with age. The skin is smooth, slightly slimy in wet weather and dry and matte in dry weather, and peels easily 2/3 of the way to the centre. The colour is a rich lemon yellow or ochre-yellow, darker toward yellow-brown in the centre and paler toward the margin. There's no greyish tinge, which sets it apart from R. ochroleuca. Mature caps have fine radial grooves at the margin.

The cap is 4 to 10 cm across, occasionally up to 12 cm. It starts convex, almost bell-shaped, then opens out flat, sometimes with a slight dip in the middle.

The colour runs from pale straw to bright egg-yolk yellow, usually darker and more ochre in the centre, and older caps fade to cream. The surface is slightly sticky in wet weather. Flat white flakes, the remains of the universal veil, sit on top, thickest in the centre. They come off easily and rain washes them away, so a cap can be completely smooth. The margin of a mature cap is grooved, with short lines like the teeth of a comb.

The gills are adnate or free, moderately crowded, thin and brittle, whitish at first, becoming ochre-cream to yellowish with age. Spore print yellow-ochre.

The gills are free or only just touch the stem, crowded, soft and white, and may turn slightly yellowish in old specimens.

The spore print is white. The spores are smooth and broadly ellipsoid, roughly 8–11 × 6.5–8.5 µm, but that only shows under a microscope.

The stem is 5-10 cm tall and 1-2 cm thick, firm and cylindrical, becoming hollow in old mushrooms. It's white to cream and quickly turns grey to grey-black when damaged, a characteristic reaction. The surface is smooth with lengthwise wrinkles, and there's no ring.

The stem is slender, 5 to 12 cm long and 0.5 to 1.5 cm thick, white or pale yellowish, smooth or finely downy, and fragile.

The ring is thin and membranous, like a little skirt, and sits halfway down the stem or lower. It doesn't last: often all that's left is a faint mark, and old specimens may have no ring at all. So a missing ring doesn't mean it isn't an amanita.

At the bottom the stem has a small rounded bulb. The volva hugs it tightly and ends in a narrow free collar at the top, sometimes broken into one or two rings or flakes. It isn't a tall sack as in the grisettes, nor a large, abruptly cut-off bulb as in the false death cap. The bulb is often sunk in the soil, so the mushroom needs to be dug up.

The flesh is firm, brittle and white and quickly turns grey to grey-black when cut, a reaction typical of the species (especially in the stem). The smell is faint, pleasant and fruity; the taste is mild, sweetish and not bitter.

The flesh is white, sometimes slightly yellowish in the stem, thin, and doesn't change colour when cut.

Faint, pleasant, fruity, neutral-sweetish.

The smell is faint, hardly noticeable. Some authors mention a slight radish note, but most field guides say there's no distinctive smell. The only lookalike you can tell by smell is the false death cap, which smells of raw potato.