This is apparently another relatively common nudibranch that is almost impossible to see. Their diminutive size (6- 7 mm) and bland colour enables them to hide rather well in their habitat of sponge and algae, rocky rubble, bryozoans and ascidians. Look closely and these brown and creamy-white Pelagellas are rather beautiful. Their mantle is framed by a ridge of brown and orange spots, their rhinophores are spectacularly disproportionate and their tails are long, thick and white and rather kangaroo-like. I’m still trying to figure out the structure of the branchial gills as they seem to be split in two but may actually be a horse-shoe. Better photos needed.
See Sea Slugs of Hawaii for a more scientific take, more photos and taxonomic information.