I'm not a mycologist, but it looks a bit like a pavement mushroom I found in Norway. But that looks bigger. Probably something like agaricus arvensis, but I'm not a mycologist and only have a slight interest in the field. The real answer is it's probably an agaricus of some type or another, but don't eat it.
Thanks for your input and narrowing it down to agaricus. Agaricus augustus seems more prevalent in our area and matches the description on local online sites. This species is apparently edible but I'm afraid this particular one is well past its prime picking time.