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Elysia sp. 12 is caracterized by its mottled orange-green colour, by small rounded tubercles with opaque white tips, and by a dark green transverse band just in front of the parapodia. The rhinophores have a dark green ring basally, the outer half is mottled orange-greenish.
It is Elysia sp. 19 in IPN at page 86:
Gosliner, Terrence M., David W. Behrens & Ángel Valdés. 2008. Indo-Pacific Nudibranchs and Sea Slugs. Sea Challengers Natural History Books. Gig Harbor, Washington. 426pp.,
let me quote the description: "This species is greenish-orange with elevated opaque white punctations. A black transverse line is present immediately anterior to the parapodia."
Elysia sp. 12 is with the total length of approximately 2,5 cm very much larger than IPN writes: 7 mm