Flabellina marcusorum
I found this nudibranch in Bahia Culebra, in the north west corner of Costa Rica. Lots of the Flabellinas look very similar. They tend to have a slender body and rows of cerata coming off their backs. Off the coast of California, Flabellina iodinea, or the Spanish shawl, is an often sighted and much photographed Flabellina.
