I see Genus Gymnopus here and is in the line of some undescribed ones
from Calfiornia.
Something along those lines:
http://mushroomhobby.com/...
Some may even be interpreted along the G. villosipes allies.
http://mushroomhobby.com/...
I have discussed some similar collections with Dennis Desjardin. The consensus is that we have quite a few such that are undescribed most likely.
D.