Here is an extinct colonial coral from the Ordovician period (approximate 440-500 million years ago). It is probably of the genus Foerstephyllum sp. and was found in the Liberty formation. Geographically that is eastern Jefferson County, Kentucky.
It reminds me of a wasp nest or bee honeycomb. I read that the vertical lines showing the stacked cells sort of work like tree rings. The wider the gap between the next wall the more plentiful food was and the narrower meant lean times.
You can see more images of this type of coral here and here.