NSR Find - Need Help Identifying

[Planko]

Wondering what this might be. Thought it was geological but the pattern might suggest other wise. Hard to see as my camera is not the best. With my jewelers lenses i see small honey comb looking structures in a line. Looking as if they are built one on top of another.  Thoughts?

 

[caldigger]

Looks like a piece of shell like big oyster or the like.

[Creek - Don]

Exogyra oyster.  Most Exogyra I found were also very worn in NSR. 

[Planko]

Guess it could be. Looked at my others and do not have the same pattern of matrix.  Others are smooth. Nothing new then.