Glaucus atlanticus, Forster, 1777 © Taro Taylor
The family Glaucidae has just two genera, Glaucus and Glaucilla and each of these genera have just one species: Glaucus atlanticus and Glaucilla marginata.
The cerata hold the stinging cells (nematocysts) which are taken from the jellyfish they eat and are stored in special sacs called cnidosacs.
This species closely resembles the other species in the family, Glaucilla marginata.
Glaucilla marginata, Bergh, 1860 © Taro Taylor
The main differences between these two species are: