Amanita volvata

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)

Annulus almost always absent
Volva present, saccate
Cap margin not striate, or striate only right at the margin
When they're young, the colored universal veil material on the cap always seems crusty to me (the brown stuff here), rather than flaky

Amanita volvata     (Peck) Lloyd