Oral arm

An oral arm is an anatomical structure of "true" sea jellies (or Scyphozoans), which belong to the class Scyphozoa. Oral arms characterize Semaeostomeae, an order of large jellyfish.

The oral arms (of which there are usually four) are located around the mouth and hold the stinging cells, or cnidocysts, which are used to inject potential prey (or potential predators) with venom.