BRIEF DESCRIPTION: All information is taken from Corner and Bas (1962). The cap of A. duplex is 40 - 100 mm wide, shallowly saucer-shaped, somewhat umbonate, grayish-brownish, pale grayish buff or pale grayish hazel, dry, with a nonstriate margin. The membranous, white, smooth volval patch covers the center of the cap.

The gills are free, crowded, and cream-white.

The stem is 60 - 120 x 7 - 10 mm, tall, subcylindrical or slightly thickened downward, solid, whitish to pallid, and exannulate. The volva is white, smooth, and nearly entirely attached to the to the base of the stem.

According to the original description, spores from dried material measure 6.5 - 7.3 x 4.8 - 5.6 µm (from fresh material, 7 - 7.5 x 5.5 µm) and are mostly broadly ellipsoid to ellipsoid. Clamps were not observed at the bases of basidia.

This species was described from Singapore. -- R. E. Tulloss