After seeing his image it reminded me of a Greenops? pygidium fragment (2 cm) I found in Clark County, Indiana. This fossil is very interesting because I found it in the area of some of Phacops trilobites posted a few days ago. This rock does not look like Jeffersonville Limestone so it might be something from the Beechwood Limestone. The fossil is white which is another aspect that is rare for the fossils I was finding that day.
Interesting side views showing the hollow area in the spines that protruded off the trilobite pygidium.