This is a small piece of an Arachnophyllum sp. coral from the Silurian aged Fiborn limestone member of the Hendricks formation. It was found near Trout Lake, Michigan. I purchased it as a comparison piece for those that I have from the Louisville Limestone of Kentucky.
The information I can find on the Fiborn Limestone indicates that, Chronostratigraphically, it is part of the Niagaran series. It is part of the Burnt Bluff group which comprise the lower to middle section of the Niagaran series with the Fiborn Limestone near the top of the group. Thus I am speculating that it is within the Wenlock epoch and Sheinwoodian stage of the UCS charts.