I think they're Cup Coral but I'm not entirely sure. The polyps weren't visible when I first purchased the Live Rock they came in on. In fact it looked more akin to barnacles on a rock. Then after a month or so in the tank they came out of dormancy (if they even do that) and began showing their tentacles. Out of curiosity I began to place mysis near their mouths which they seem to welcome. After about a month the largest one of the bunch has nearly doubled in size. And the other 'dormant' cups appear to be growing tentacles as well.
