I again dug out the mushroom field guide, but this is getting really hard! I'm guessing the second one on the underside is covered with small white pores, maybe 4 to 6 per mm. This would make it one of the Polypore family, perhaps an "Artist's Conk," Ganoderma applanatum. If so, the white pore surface bruises easily, and a detailed drawing can be etched into the serface that on drying will remain permanent. Then again, it could be something entirely different. I can't find anything in the book that looks like the first ones, though I've seen plenty of them around in the wild, so they must be quite common. Maybe they are just haven't grown up enough yet to have their picture in the book.