Here is a Silurian index fossil called Halysites or chain coral. It is part of the hands on exhibit in the Discovery Gallery at the Louisville Science Center where I volunteer. The specimen does not have a label as to where it is from but it looks like ones I find in the area so it could be from Jefferson or Clark counties in this area.
I found a description of this coral in a a book stored at books.google.com entitled "An Introduction to the Study of Fossils (Plants and Animals) by Hervey Woodburn Shimer published in 1914. From pages 137-138, "Coral compound, composed of long, laterally compressed corallites, and covered by peritheca. Septa absent or represented by spines; tabulae numerous. Between each pair of corallites is a small tube. Budding occurs only from one side and the young corallites remain in contact with the parent by a constricted edge, thus forming chains, in which each corallite is a link (whence the common name, "chain-coral," from the Greek halysis, chain)."