Phylliroe bucephala is a parasitic species of pelagic nudibranch, a marine gastropod mollusc in the family Phylliroidae.
This species of nudibranch is transparent with its guts visible through the laterally flattened body. It has a tail and two long smooth rhinophores. It feeds on jellyfish and plankton as an adult. The juveniles parasitize Zanclea medusae.[1]