It looks like a Celtic labyrinth motif – but it’s not. Can you name this thingy?
Here’s a hint which won’t help you much: Experts refer to it as a “broad-collared enteropneust”.
The Smithsonian can help you understand them a bit. An encyclopedia won’t help much, but the University of Washington goes a bit further… but you can also find out a little more about some recent collections of these sorts of… thingies.