BRIEF DESCRIPTION: The data in this description is almost entirely dependent on the protolog and a study of the type. The cap of Amanita humboldtii is usually free of volval remnants, 35 - 60 mm wide, subumbonate to depressed, with a strongly striate margin; it is dull fuscous brown or ranging from dark orange-brown to fuligineous in the center and orange-brown to medium dark brown in the outer part. [Note: the description seems to mix the present species with A. fuligineodisca Tulloss, Ovrebo & Halling. The reader should assume that the color of A. humboldtii is "dull fuscous brown."]

Gills are free, close, white in side view, and about 5 mm broad, sometimes marginate and then having edge white or concolorous with pileus on the portion of the gills closest to the cap margin. There is no information on the short gills.

The stem is 60 - 180 × 6 - 11 mm, entirely white or white on the lower half and pale orangish tan on the upper half, exannulate, and has a membranous sack-like volva at the base. Singer describes the volval sac as (for example) 20 × 12 mm high. The volval sack may be white, cinnamon, or orange; it is largely free from the stem.

The spores measure (10.2-) 11.0 - 14.0 (-15.5) × (9.0-) 9.8 - 13.0 (-13.3) µm and are inamyloid, globose to subglobose or (infrequently) broadly ellipsoid. Clamps are rare or absent at bases of basidia.

Amanita humboldtii is known from Andean Colombia, occurring with oak. Apparently, it is not frequently collected. One collection that might be attributable to this species has been sent me from Costa Rica. I have never seen fresh material of this species.