There are two corals that occur locally. Stereostylus is a common solitary horn coral in Pennsylvania. These two specimens show perhaps the same species. The top piece on polished limestone is a cut cross section. The bottom piece is an eroded end sticking out of stone. The shell material eroded past the matrix, showing an interesting pattern.
Further Reading on Corals
- Digital Atlas of Ancient Life – Article
- fossilworks – Stereostylus