This is Streptaster vorticellatus, a member of the Edrioasteroidea class. The Edrioasteroidea is an extinct class of echinoderms that lived all the way on from the Ediacaran period 600 million years ago! However, Streptaster vorticellatus lived “only” 450 million years ago, during a period called the Ordovician. The body plan for this class was simple: a main body (theca), composed of many small plates, a peripheral rim for attachment, and (in some species) a pedunculate zone for extension and retraction.