Below are 3 views of the same fossil.
I did not think to include a size reference item in the pictures, but you should know the fossil is about 8 inches long and 3-4 inches wide.
It was bigger once, but I took it to school to show the kids...and you know how that goes...naughty rascals
It came out of a shallow lime rock pit and probably only dates back to the Eocene.
I won't be near a computer until late afternoon at the earliest, but I will post an answer ( ...and check yours) at that time.