It's a Lucapina species, most likely Lucapina aegis. There are a few other options, but you'd have to have the mantle withdrawn to ID it. These are the ones that people often accuse of eating their softies, or other things that many aquarists don't want eaten. Their diets are probably broader than most of the fissurellids, and no doubt also include whatever they can scrape off your rocks.
I'm afraid I don't know much about these guys except a little hearsay. I just know that most people I talk to know nothing about these guys. I was hoping to hear that they aren't too awful because I just think they are as cool and bright as can be. I'm not going to evict any until I see a problem. I have never had any pest eat my corals (yet ), and until that happens...they're staying!