[1] Members of the order Rhizostomeae are collectively known as "root-mouth jellies" and are very diverse.

They do not have tentacles or other structures at the edge of the bell, instead they have eight oral arms which fuse together to form the manubrium, a central organ with the mouth at its tip, resembling an elephant's trunk.

The edge of the bell bears flaps known as lappets and in the niches between these, there are usually eight rhopalia (sensory organs).

Some semaeostomids are suspension feeders, but others supplement this with prey such as small fish, crustaceans, worms and other jellyfish.

The pulsating action of the bell is linked by a nerve ring to the sensory inputs received by the rhopalia.