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It might be a strange yellowish-orange variant of Phyllidia willani or of Phyllidia sp. 3 in IPN at page 292, which differs by the opaque white granular appearance and by transverse black lines or patches.
Pretty similar are:
Phyllidia ocellata which is very variable in colour, but has usually a yellow-orange ground colour of the mantle, and has large black rings,
Phyllidia babai which has a white granular appearance and black rings.
Phyllidia exquisita which has a pale bluish granular background colour, black swirls, and yellowish-orange pigment at the mantle margin
Phyllidia willani which has a white granular appearance, and lacks orange pigment at the mantle margin
I can't tell for sure how to distiguish the phyllidiids with the whitish granular appearance:
Phyllidia babai, Phyllidia exquisita, Phyllidia willani, Phyllidia sp. 01 and Phyllidia sp. 3 in IPN at page 292. I guess they are variants of one species.
Bill Rudman thinks Phyllidia babai, Phyllidia exquisita, and Phyllidia willani to be variants of the very variable Phyllidia ocellata.
How to cite:
Köhler, E. (2016), published 28 January 2016, Phyllidia sp. 01 Genus: Cuvier, 1797
available from http://www.Philippine-Sea-Slugs.com/Nudibranchia/Euctenidiacea/Phyllidia_sp_01.htm