This is the Inky Cap mushroom, called such because it autodigests from the outside edge inward - and writers actually used the black liquid as ink. It grows on wood, often buried wood, in tufts consisting of several inky caps. They are supposed to be edible, but I am not sure how one cooks them without inviting a black mess. Anyway, one reason for not eating them is that they contain coprine, a toxin very similar to the active ingredient in Antabuse, the drug given to alcoholics to discourage them from drinking. If you consume Inky caps with alcohol you will feel very sick to your stomach and probably will lose your dinner. These effects can even be triggered days later with a sip of wine.