Ivory Bonnet

The cap of A. flavoalba is 1–2 cm (0.4–0.8 in) in diameter, conical when young, becoming somewhat bell-shaped, broadly conic or at times nearly convex. It may develop a papilla (a nipple-like structure) in its center. The cap margin is initially pressed against the stem, but in maturity either flares out or curves inward slightly. The cap surface is smooth, moist, and partially translucent, so that the outline of the gills underneath the cap may be seen. The mushroom is hygrophanous (changing color as it loses or gains moisture), being cream-buff to yellowish initially, with a paler (almost white) margin, and fading to buff in the center and yellowish-white along the margin when dry. The flesh is yellowish to white, thick under the disc but otherwise thin, moderately fragile, and without any distinctive odor and taste. The gills are ascending and somewhat hooked or toothed, narrow at first but becoming rather broad (2.5 mm and becoming 3–4 mm). They are nearly equal in width throughout or slightly ventricose in age, with a spacing that is close to subdistant. About 18–24 gills reach the stem, with two tiers of lamellulae (short gills that do not extend fully from the cap margin to the stem) that may develop veins running between them. The gills are white to creamy-white with edges that are even and whitish, and waxy in appearance and consistency. …

The fruit bodies of Atheniella flavoalba grow scattered to densely gregarious in mossy pastures, needle beds under conifers, or on humus in oak woods during the autumn. The species is common in old grassland in Europe, but less common in North America though sometimes occurring in large quantities in certain localities. In the United States, it has been collected from Colorado, Idaho, Michigan, North Carolina, Oregon, Washington, Wyoming, Florida, and Kansas. It is also found in Israel. The species is listed as "Least Concern" in the Danish Red Data Book. Atheniella flavoalba is considered inedible.

The specific epithet flavoalba ("yellow-white") is a compound of the Latin adjectives flavus ("yellow) and alba ("white").