Moira atropos (Lamarck) is a Caribbean heart urchin, ranging from the
Carolinas through the West Indies.  There are a number of other species (and
other genera) of heart urchins from various localities around the world.  I
have the family as Hemiasteridae, but that family does include the genus
Schizaster; therefore the family may be known alternatively as Schizasteridae.
The class is indeed Echinoidea.
Paul M.