It's for sure NOT a sand sifter. The first thing that comes to mind is a fromia star, as it has too many bumps to be a chocolate chip. You should return it, as many sea stars (proper term) are not reef safe. I messed up and bought a chocolate chip (my wife's idea) without researching it. After losing a couple of prize mushrooms and ricordeas, it went back to the LFS. This is what a sand sifting sea star looks like. It's grayish-white body is fairly smooth with small black patches scattered across it's body/legs.