Agaricus rubescens (Pers.) Fr., Systema Mycologicum 1: 18 (1821) [MB#480031]
In California this name was regularly applied to A. novinupta until it was recognized as a separate species.
I’ve slowly been trying to remove author “misspellings” from the database, as people bring them to my attention by attempting to correct them. From Rod’s comment, it looks like “Pers. : Fr.” is correct in this case.
Previously the sanctioning by Fries did not appear in the author citation.