what is it?

[Donnajayne]

Thats we thought when we 1st saw it..fish shape

[Donnajayne]

[CliffJ]

Hi Donnajayne,
   That looks like a natural piece of limestone that has broken and eroded into a vaguely fishy shape. It does not appear to be worked,ground, pecked, or flaked. Someone kept it because of that unusual shape.
  There may have been markers used in some areas, but this is not one of those.
  Cliff

[SDhunter]

I agree with Greg and Cliff,  Something fishy going on!