I checked out the The Geological Society of America Memoir 93, Silurian and Devonian Corals of the Falls of the Ohio by Erwin C. Stumm from...

Here are some bubble looking structures found at a road cut at Blankenbaker Road in Louisville/Jeffersontown Kentucky. There are a lot of ...

Here is a rock piece with bubble like shapes and also some straight line projected out radially. It could be piece of brachiopod or a bunch...