Re: Scyllaea pelagica? from sthn Queensland

Dear Gary,

Every time I see one of these fascinating animals I get more confused trying to identify them to the genus level. There are really no external features to separate Scyllaea and Notobryon. Internally, Scyllaea differs in having a central tooth in the radula, while Notobryon does not. My feeling is that this is probably Notobryon wardi which was described from Queensland, Australia. It doesn't help that it was described from preserved animals so we have no idea of the colour or living shape of the original specimens.

At present Scyllaea, as represented by S. pelagica, can be identified externally by the dark brown band along the side of the body, just below the mantle edge. On those grounds I think I would rather identify your animal as Notobryon. Of course the only way to be sure is to look at its radula. Whatever it is, it is a wonderful find. One of the reasons we have trouble with this group is that Scyllaea pelagica appears to be the only species which is regularly encountered. This is because it lives on floating weeds and often washes ashore after storms. If it were not for the radular difference, I would suggest we consider Scyllaea and Notobryon to be one genus, but until we have many more specimens - preferably with photographs or drawings of them alive - we won't be able to get past the impasse created by Odhner's study of preserved animals many years ago.

• Odhner, N.H. (1936)  Nudibranchia Dendronotacea - A revision of the system. Mémoires du Musee Royal d'Histoire Naturelle de Belgique, series 2, fasc. 3, 1057-1128. (Pl. 1)

Best wishes,
Bill Rudman