Bulla occidentalis A. Adams, 1850  -   Western Striate Bubble And Fireworm Predator

This Bulla occidentalis, when initially discovered, was being devoured by an adult "Red-Tipped Fireworm" Chloeia viridis Schmarda, 1861 (Class Polychaeta).
Shortly thereafter, the juvenile fireworm (pictured in the above link), crawled up to the adult fireworm at which point it crawled away and the juvenile took its place and began feeding on the now partially consumed Bulla occidentalis.

    Photographed by Anne DuPont while SCUBA diving at Lake Worth Lagoon near Peanut Island, Palm Beach Inlet, Palm Beach Co., Florida 6/10/2010 | Underwater photograph copyright 2010 by Anne DuPont (Delray Beach, FL).