"Note the red longitudinal stripe down the middle of the back which is characteristic of this species, and also the tapering pointed oral tentacles (flattened and paddle-like in Flabellina riwo, Flabellina bilas and Flabellina bicolor). There would have been another stripe along each side of the foot, but they are not visible in this photo because of the angle it was taken from."
Comment from Richard Willan
Note the red longitudinal stripe down the middle of the back which is characteristic of this species, and also the tapering pointed oral tentacles (flattened and paddle-like in Flabellina riwo, Flabellina bilas and Flabellina bicolor). There would have been another stripe along each side of the foot, but they are not visible in this photo because of the angle it was taken from.