re: I found a rock! Please help me identify it

Petrified calcified clam shell of some sort given the sloughing and flaking imho. Not an Indian artifact imho. I've got some various prehistoric knives that, at first glance, might resemble that but that's not the type of stone native americans would waste their time trying to use as a knife.

I live well below the fall line here in SC, in beach sand, and we occasionally see things like that pop up ... similar in nature. Calcified clam shells.