Hi, Bob
You seem to have american parasols, scientifically known as Lepiota americana. The genus Lepiota is distinguished by free gills (that is, they stop before they reach the stem), a ring, white spores, no basal features, and scales that are part of the cap - - that is, if you try to peel the scales away from the cap, flesh from the cap gets torn up with them. The similar-looking genus Amanita has a cup or scales at the base of the stalk, and cap scales that peel away cleanly. Those are very poisonous, accounting for 90% of all the mushroom fatalities in the US. Many of the small Lepiotas are deadly, too; but most of the big ones are tasty edibles! (That was ordered to make you cautious)
L. americana is distinguished from the others by bruising maroon (as in your photo) and having a stalk that is fatter in the middle than at either end. It's quite delicious sauteed in butter, but yours seem to have "gone by". Give me a call when they come up again, and we'll make an appointment to have me check them out and confirm their identity.
L. americana is listed as "common" in most books, but I had never seen them until a few came up in Hyde Park about six years ago. I got very excited and took almost a dozen photographs of them. Now they're everywhere in quantity, and probably the most common good edible in the city proper, since they'll grow anywhere that there's wood chip mulch. The stalk shape and color change are quite distinctive. Our local version, when fresh, bruises yellow, and changes (over about ten minutes) to purple and then the "orthodox" maroon. Someday, someone will get around to naming it as a new species. Until then, it just makes it easier to identify...