Can these 3 be ID’d?

[butchndad]

Tiny items, 1/2 - 1/4 inches, picked up in Big Brook that caught my attention and warranted being brought home. Teeth? Bivalves? Concretions?  As always thank you for sharing your expertise

[aek]

I've never been to big brook, but the first 3 look toothy. 1 and 3 probably stingray teeth but I could be wrong. 

[Rockwood]

The last one looks as if it is fossil related. Something like mold fossils of shells perhaps.

The first ones I'm afraid are the all too common concretions found in the NJ brooks.