We used to call this Gymnodoris plebeia based on a paper on Hawaiian dorids by Kay & Young (1969). Sea Slugs of Hawaii does not consider it to be G. plebeia, but figures it as Gymnodoris sp. 6. Whatever the name, we see the same species in the Marshall Islands.
Links:
Sea
Slugs of Hawaii
Marshall Islands Sea Slugs
Created 20 April 2009