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DescriptionA semi-transparent nudibranch with numerous swollen cerata, each with a thin dark thread of digestive gland running through the centre. The tips of the cerata are coloured with an iridescent bluish-white pigment, and similar pigment patches are found on the back, between the cerata and in the head region. The rhinophores have lamellae set at an angle, giving the appearance of spiral grooves. Between them is a cockscomb-like structure called a caruncle which is unique to Janolus species. A large species, growing to at least 75mm.