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None of my books has Macrolepiota subrhacodes listed as a species, and searching the Internet only yielded abstracts that (for my purposes right now) only confirm that the species exists.
Certainly the specimens strongly resemble M. rhacodes (=M. rachodes), although the habitat is wrong. When describing finding them, one thing in common is that they are always found near trees, and never in lawns as those are (at least here in Colorado). In fact, finding them in lawns is used here as an indicator that your mushrooms are very probably Chlorophyllum molybdites.
I know you know how to ID C. molybdites, so I needn't go into that.
Bruising reactions would be a good thing to obtain, to make sure you haven't got the very similar Lepiota brunnea, which causes gastric upset. L. brunnea bruises immediately brown.