Dryad's Saddle (Polyporus squamosus), or also called Pheasant's-back Polypore.

I found many on the same tree where I had spotted one last year. This specimen is small, maybe six inches across, but the largest on the same tree trunk I estimate to be 12 inches across, maybe more. I cannot get to these mushrooms, the embankment along the trial is too step.