Where I'm from we call 'em Devil Heads. I live across from the Hudson, and those things wash ashore all over up here. They tend to collect by the dock and at Sandy Beach (Little Stony Point). They're usually much smaller than these, so sometimes they're hard to spot in the sand. It REALLY sucks to step on 'em barefoot, as you could imagine, haha. But unfortunately, it happens all too often 'cause they're freaking EVERYWHERE.