Mold fossil of a brachiopod . The rock measures ~55 mm (2.1 in) long, ~42mm (1.6 in) wide and ~27.5 mm (1.08 in) thick. The fossil Measures ~6.6 mm (.26 in) tall and ~7.8 mm (.30 in) wide. This fossil dates to the Devonian Period (416-359.2 million years ago). I believe the rock is limestone.
Rocky bottom of man-made lake. Pymatuning Lake. Andover, Ohio, USA
The extreme close up pictures were taken with a Digital Blue QX5 USB microscope at 10x power.