Here Caleb and I are looking at two specimens of Gymnopus dryophilus (formerly Collybia dryophila). Caleb's specimen is younger than mine. Still, even in its youth the Oak-loving Collybia (Gymnopus) exhibits a wavy cap margin. The warm brown cap is moist and the gills are off-white, free to near-free and closely-spaced. The spore-print is whitish. Gymnopus dryophilus grows on the ground in woods, although sometimes it grows on decomposed soft wood fibers. Our specimens were, appropriately, found in leaf litter under oaks. (See the next two images of Gymnopus dryophilus).