On a recent walk in Stradey Woods, Llanelli, I saw these bracket fungi around the base of an Oak tree. Another bracket was at the far side.
The surface is uneven and bumpy, white at first but turning more brown after about a week.
Pores are quite small and the spore deposit is white as seen on vegetation beneath the brackets.
For a long time I have puzzled about an enormous bracket at the base of an Oak close to the home of Janet and Keith Crowden near Llandeilo. The last photo is this one, old brackets remaining although no fresh ones for the past two years. This must be this species which develops huge brackets and is uncommon. From the specific name, it is found on Ash but equally frequently on Oak it seems.