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This species was posted on 06 October 2012 at these websites as Pseudocerotidae sp. 17 Family: Lang, 1884, because my best guess was that it should be placed in the family Pseudocerotidae Lang, 1884.
This picture was identified on 22 August 2013 by Sudhanshu Dixit at the facebook group Marine Flatworms.
Let me quote Marcela Bolanos' description at http://polycladida.lifedesks.org/pages/3213: "A black or chocolate background with small and regular white dots over the dorsal surface, and larger and evenly distributed larger dots arranged in flower-like clusters. The tips of the tentacles are white. The ventral surface is dark blue or grey. The body is raised on the longitudinal median line and the tentacles are highly developed, square, inflated with deep lateral ruffles."