Click the thumbnail photos to enhance!
It is characterized by highly branched tan gills and by dorsal tubercles.
It is most probably Marionia sp. 2 in IPN at page 337:
Let me quote the description: "This species is similar in appearance to Marionia arborescens and Marionia sp. 1, with highly branched gills and dorsal tubercles. The gill branches are more curved in this species and there is dense opaque white pigment on the notum."
I agree, it looks very similar to Marionia arborescens, there is a large whitish patch at this picture between the gills, Marionia arborescens is greenish brown, IPN: "Opaque white covers some of the tubercles." - I am not convinced that they are distinct species, I will keep them seperate for now.
Pretty similar are
Marionia sp. 10, which differs by a pale tan body, and lacks prominent tubercles.
Marionia sp. 15 which differs by a pale tan/whitish reticulate pattern
Gosliner, Terrence M., David W. Behrens & Ángel Valdés. 2008. Indo-Pacific Nudibranchs and Sea Slugs. Sea Challengers Natural History Books.
Gig Harbor, Washington. 426 pp.
How to cite:
Köhler, E. (2016), published 2 December 2016, Marionia sp. 08 Genus: Vayssière, 1877
available from https://www.Philippine-Sea-Slugs.com/Nudibranchia/Dexiarchia/Marionia_sp_08.htm