Ok, here's a challenge folks. A question with no photo. I'm normally ok with fungi, but this has me stumped.
Collected late May/early June, from what was a willow/alder woodland, and is now a lot of stumps and piles of chippings. The fungi were growing abundantly on the chippings piles, and nowhere else. They key out as genus Agaricus, and I'm certain that is what they are, but I can't get them to species. Either the habitat or the season is wrong. They are browner than a field mushroom, and had no obvious smell when fresh. Now that they are dried (I kept them) they have a pleasant mushroomy smell. When cut or bruised they did not turn yellow or red. Cap was not scaly. Stem with a large and obvious ring. No volva, and gills dark, with a dark brown spore print. Growing in loose clumps.
Based on the pictures in Roger Phillips book, the best match for general appearance is Agrocybe praecox, but it isn't that because of the ring, and the gill colour was much darker.
Habitat says something like Agaricus bitorquis, but the appearance isn't right. Appearance is rather like Agaricus augustus (The prince) in colour, but it wasn't scaly. Horse mushroom is also possible, but wrong habitat and time of year. I'm stuck.
This is really frustrating me, as whilst I am certain that this must be an edible species, I have a personal rule (based on a bad experience many years ago when I took a chance and got it wrong) that I won't eat any mushroom that I cannot identify to species with absolute certainty.
Any bright ideas?
(As they are dried out now a photo is a bit useless)