Halgerda cf willeyi
Hachijo Island, Japan. Upper 60mm long, Lower 50mm. PHOTOS: Rie Nakano.
This differs from Halgerda willeyi in having a yellow border to the mantle. Apparently variable in colour with yellow lines on mantle sometimes being absent.
See Rie Nakano's message below.
• Eliot, C.N.E. (1904) On some nudibranchs from East Africa and Zanzibar. Part III. Dorididae Cryptobranchiatae, I. Proceedings of the Zoological Society of London, 1903(2): 354-385, Pls. 32-34.
Rudman, W.B., 1999 (November 24) Halgerda cf willeyi Eliot, 1904. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/halgsp3