Alveolites is a tabulate coral that is common within the Silurian to Devonian rocks of North America. However I often confused it with Cladopora because I wasn't examining my specimens close enough. Below are some specimens of Alveolites goldfussi that I found in Arkona and came from the Hungry Hollow member of the Widder formation (Middle Devonian in age).
A second specimen that shows the "sideways" growth a little better.
When looking at the calice growth and arrangement patterns it reminds me of fish scales and that is what I look for in the field now.