My (possibly poor reading of) the audobon guide, my instinct, and my foraging friend tells me these are oysters.

Definitely not oysters. Possibly Tapinella atrotomentosa.

In my experience, the only way to "really know" a mushroom is to find it repeatedly, have it in your hand, smell it, and have someone next to you who really knows their stuff and talk to them about the mushroom in your hand, and learn that way what characteristics to look for. Then find it again, identify it yourself, confirm with an expert. Repeat until you don't have to ask.