Goniodoris nodosa (Montagu, 1808): a new "old" species to the Belgian marine fauna

A 3mm long specimen of Goniodoris nodosa (Montagu, 1808) (Mollusca, Gastropoda, Opisthobranchia, Nudibranchia) was discovered amongst samples determined as Acanthodoris pilosa (Abildgaard in Müller, O.F., 1789) in the century-old collection of marine organisms gathered by Gustave Gilson and held at the Royal Belgian Institute for Natural Sciences, Belgium. This discovery constitutes the first record in the Belgian maritime zone. G. nodosa should be considered a naturally rare species in this area.