Matt D sent this picture which shows a Violet Toothed Polypore growing on a Tinder Polypore.  Below is a description in his own words.

"My buddy Jeff found it -- he is a newbie, but I took a look at it, and was pretty sure it was a Trichaptum biforme growing on an old Fomes fomentarius....though, admittedly, I could be wrong about it. It is not uncommon for a species to grow on itself, using itself as a substrate -- but I think it is much less common for one species to grow on another. Larry Millman saw it and said he'd never seen anything like it before, and Leon Shernoff may be putting it in an upcoming Mushroom Journal, and commented that even very common mushrooms can behave mysteriously.

It was found growing on a white birch out in Leominster State Forest."