Collection location: San Jose, Santa Clara Co., California, USA [Click for map]
Not sure of the id even at the genus level. Found growing in my brother’s backyard. A large japanese maple and a couple of pines were nearby. The young caps had a noticeable cortina. Between that and the cap and gill colors it seemed like it was most likely a Hebeloma. I would have expected the gills of the older ones to be more orange if they were Cortinarius. Doug Smith took the collection that evening and may have done some more work with it.