This is an agaric with medium to large cap; vivid yellow, brown at center; no black streaks or fibrils. Gills yellow.
broadly convex or nearly flat, with an inrolled margin at first; expanding to broadly convex or flat, often with a broad, low, central hump. Pale yellow at first, then greenish yellow to vivid yellow and usually remaining yellow on margin but gradually becoming brown from disk center outward. Flesh thick, firm; white or tinged with yellow under cuticle. Gills notched around apex of stem, close, broad; edges become ragged with age. Gills attached to the stem, often by means of a notch; close, bright yellow, not staining when bruised. Stem
more or less equal, or enlarged at base; solid or hollowed in age. Surface smooth to fibrillose; pale to light yellow.
Be sure to distinguish from Tricholoma sulphureum and from Tricholoma sejunctum, both of which are poisonous.
Tricholoma equestre (Tricholoma flavovirens)
on the MushroomExpert.Com Web site.