[Cubo-/Scyphomedusae] Thick tentacle-like structures around the mouth in scyphomedusae, typically four or a low multiple. In rhizostome medusae the four are fused near the base and they immediately fork each in two so that there appears to be eight. In semaeostomes they are free along their entire length, and four in all species. Also known as oral arms. Coronates and cubomedusae lack them.