I found several varieties of Devonian corals, including Pachyphyllum, Hexagonaria, Thamnopora and Alveolites near Superior, Arizona. Check out this Pachyphyllum woodmani that reminds me of the painting The Starry Night by Vincent Van Gogh. The painting also inspired a great song by Don McLean:
https://m.youtube.com/watch?v=dipFMJckZOM
Pachyphyllum lack common walls with their neighboring corallites. The septa grow in a curving manner towards each other meeting in a slightly irregular fashion.