This fossil is on display at the Falls of the Ohio State Park Interpretive Center. It is thought to be an Aulocystis (?) procumbens tube coral growing on top of a Favosites turbinatus tabulate coral fossil. They existed in the Devonian time period and were found in the Jeffersonville Limestone of Clark County, Indiana, USA.
Very neat specimen put on display in the new exhibit there. If you get chance, try to visit as they have quite a few fossils on display.
http://fallsoftheohio.org/
