Hallucegenia was a genus of animal that first appeared in the Cambrian explosion. They were named and described by Simon Conway Morris in 1979.
Hallucegenia in "Worlds Enough, and Time"
Hallucegenia was one of several animals in an aquarium that a family of space travelers brought with them on their vacation to Earth. Despite the father's misgivings, he allowed his daughter to empty the aquarium into the oceans, thereby spurring an explosion of life.