A type of nudibranch (order Nudibranchia) in which the mantle is extended into long finger-like projections, the cerata (sing: ceras), rather than a feather-like external gill on the dorsal surface. The cerata contain branches of the digestive gland. The tips of the cerata contain cnidosacs which usually store nematocysts that are obtained from ingested cnidarian prey, such as hydroids, sea anemones and soft corals. If threatened, the nudibranch is capable of discharging these stinging cells through a terminal pore in the ceras. This action is an effective deterrent to predators.