Amanita wellsii

This is a key to gilled mushrooms, that is, mushrooms having a definite cap with a fertile surface consisting of gills. The fruiting body usually also has a stem, although that may be lateral or absent (usually, then, the mushroom is growing from wood). You can use this key to identify mushrooms that you find.

Fruiting body containing fibers (usually in the stalk)

Fruiting body having a combination of some of the following characteristics:
Stalk growing out of a cup of cottony tissue called a volva (all white-spored mushrooms with a volva go here)
Cap with scattered patches or flakes of the same sort of tissue as the volva (see second picture), easily peeled off
Annulus (skirt-like ring on stalk)

All yellow-capped Amanitas can go here
All Amanitas with concentric, toothed rings around the base of stalk definitely go here
No volva; basal bulb sometimes small, often rimmed in one way or another
Universal veil generally leaves remains on cap as small scattered patches

Base of stalk slightly and smoothly bulbous
Cap some shade of yellow; less than 5" across, and usually less than 3
Annulus usually present, but it may be fragile and easily lost, or plastered to the stem and overlooked

Amanita wellsii     (Murrill) Saccardo