BRIEF DESCRIPTION: The cap of A. demissa is 15 - 35 mm wide, campanulate to plano-convex, becoming plane at last, sometimes slightly umbonate, sometimes slightly depressed at the center, grayish umber or umber-gray, paler toward margin, slightly viscid, with a 1/3 striate from margin toward the center. The flesh is thick over the center, soft, and white. The cap is sprinkled with minute, soft, scurfy, fuliginous, easily separable particles that form conical warts in the center.

The gills are free, not crowded, thin, and white.

The stem is 25 - 50 x 2 - 3 mm, brittle, attenuate, and hollow. Volval remnants are present at the base of the stem.

According to the original description, spores from dried material measure 6.4 - 8.5 (-10.1) x 4.7 - 6.4 µm (from fresh material, 7 - 9.5 x 5 - 6.5 µm) and are broadly ellipsoid to ellipsoid (occasionally, subglobose). Clamps were not observed at the bases of basidia.

This species was described from Singapore.