April 9, 2007
From: Colin Teo
Locality: Malapascua, 13m, Philippines, 21 February 2007. Length: 4 cm. Photographer: Colin Teo.
firstname.lastname@example.orgTeo, Colin, 2007 (Apr 9) Halgerda elegans from the Philippines?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/19692
Your animal looks very similar to Julie Marshall's photo [#2077] which we have identified as Halgerda elegans. There are two species of Halgerda with this radiating fringe of black lines around the mantle edge. In H. elegans the lines on the innner part of the mantle are yellow and the background translucent white, while in the other, H. albocristata, the background is yellowish and the lines are white.
However I still suspect there is some sorting out still to be done in this group. For example two messages [#2688, #8147] have photos of animals I have tentatively identified as H. willeyi, but are probably the same as your animal.
Sorry I can't be more definite