This is the heart (and brain and pretty much anything that’s not an arm) of a brittle star, as sketched for Echinodermata, a study of the sea urchins, sand dollars, sea stars and close relatives collected by the Michael Sars Deep Sea Expedition in the North Atlantic in 1910. It was published by the University of Bergen in Norway.
I happen to know that Bergen is where Edvard Grieg lived, so there’s a good chance that James Grieg, the creator of this report, is related to the fellow who wrote “In the Hall of the Mountain King.” And here, we have creatures more fantastic than any trolls, dwarves or fairies dreamed up for Peer Gynt.