http://mysite.verizon.net/despen/mushroom.jpg

===C. butyracea is terrestrial. I suspect they are Pleurotus.====

Perhaps a better view for ID purposes:

http://mysite.verizon.net/despen/mushroom2.jpg

===If they're not Pleurotus I don't know what else they'd be. The gill shape
is wrong for Clitocybe, which'd be my biggest worry AFA edibility. Most
often Oysters have white or whitish gills (caps as well), but the books say
they can be gray-tinged, as these seem to be. I've never encountered them.