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Very similar are:
Phyllodesmium hyalinum which differs by the cerata, basically smooth, apically nodulose and curved, and by the position of the position of the anal papilla.
Phyllodesmium tuberculatum which differs by the bluish grey colour, and by rounded tubercles on the cerata.
More information on Phyllodesmium crypticum are on Bill Rudman's Sea-Slug Forum!
How to cite:
Köhler, E. (2016), published 18 December 2016, Phyllodesmium crypticum Rudman, 1981
available from https://www.Philippine-Sea-Slugs.com/Nudibranchia/Dexiarchia/Phyllodesmium_crypticum.htm