These particular Agaricus fruit every summer and/or fall after some good rain in the woods at Westwood Hills Nature Center. The two in the foreground are younger specimens that haven't fully opened up yet. I think they might be A. silvicola. Below are some pictures that feature identifying characteristics of the genus, and features that lead me to believe it to be A. silvicola.
Agaricus mushrooms have a thick veil covering their gills at first. According to most guides, the veil of A. silvicola usually shows a cogwheel-like pattern, and is white with yellowish stains.
Fawn Mushroom - Pluteus cervinus
Tough little mushroom, growing from wood chips. Maybe a species of Marasmius.