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There is a picture of the holotype from Guam at the OKINAWA Slug Site as Fryeria larryi, which has a pale yellowish colour. This species is very rare, there are only a few pictures of it at the web, all of them are almost white with a yellowish tinge, not yellow. There are some pictures of it from the Kerama Islands, Japan, fom Kagoshima, Japan, and as Phyllidia zebrina from Suruga Bay, Japan, and a picture of Phyllidia cf. larryi from Hawaii.
Pretty similar is
Phyllidia zebrina Baba, 1976 which differs by the position of the anus (in the posterior dorsal midline) and by small rounded tubercles.
Let me quote Robert F. Bolland:
"There is apparently a bit of confusion in some of the literature as to the correct species name of this little Phyllidiid. In addition to the original name given by Brunckhorst (1993), two names have been applied, Phyllidia larryi and P. zebrina. Both descriptions of these two animals were based on a single specimen, so of course nothing is known of variation within the species. Current workers refer to the species as Phyllidia larryi (Gosliner, T.M., D.W. Behrens, & Á. Valdés, 2008) and not P. zebrina."
Phyllidia larryi was formerly placed in the genus Fryeria due to its lack of a dorsal anus. However Fryeria has now bean synonymized with Phyllidia.
More information on Phyllidia larryi as Fryeria larryi are on Bill Rudman's Sea-Slug Forum!