I had the opportunity to visit the fossil site at Hungry Hollow near Arkona, Ontario twice this year. On my most recent trip, in October, I brought back a bunch of horn corals as they are fascinating to look at. They are as common as acorns in the fall but have an endless array of shapes.
Here is a coral that I think is Heterophrentis sp. with a typical profile showing the horn shape that gives Rugose corals their nickname. Note the small hole on the side that may be evidence of predatory behavior by a boring snail.
Below is a Eridophylum coral that has three smaller Eridophylum budding along one edge. They could represent asexual reproduction by the coral or possibly colonization by young polyps of an dead coral. In either case they didn't have long to live and were buried by the next storm.
A fascinating fossil, this coral has a small Brachiopod called Cryptonella attenuata that is lying on the calice. I don't know if this represents a life position for the Brachiopod or if it's just the juxtaposition created by burial.
This coral had a rough life. It started out upright but then got flipped over during a storm. It managed to recover and once again grew upright.