I have given this some thought since Dimi presented his pictures – the brownish discolouring on the gills was a little disturbing. A better match with that feature is actually Lyophyllum favrei (has been named Calocybe favrei(!).
The spores in this collection fit well too, 3.5-4.5 × 2.8-3.5µ.
It was described from Central Europe not too long ago, and is VERY rare.
If it is Lyophyllum favrei, I’d say it’s remarkable. Is it known from the USA, or does it have any “sister” species here?
