Biology/Natural History: Feeds on several sponges, among them Halichondria panicea and representatives of the genera Myxilla, Mycale, Stylissa, Tedania, Craniella, and Syringella. Eaten by the rose star Crossaster papposus. Eggs are deposited in areas of high current. Eggs are laid in large masses of thin, wide ribbons. Egg ribbons may be found year-round in Washington state. The ribbons form oval spirals with a fluted edge and are attached by one edge to the substrate. Each capsule in the ribbon usually contains 8 to 12 eggs. Named after biologist Nils Hjalmar Odhner.