"The population in the Red Sea always has this wavy (instead of ocellated) pattern on its mantle and it has received the name Phyllidia undula for this distinctive pattern (so Phyllidia undula can be used as a regional form name). But this same pattern can also be found, albeit rarely, in “normal” ocellated populations in the Indian and Pacific Oceans, so Phyllidia undula cannot be considered as a species separate from Phyllidia ocellata."