Typically inhabitants of deeper waters, the jelly fishes in this order generally have conical or flattened bells and are characterised by the presence of a coronal groove midway between the centre of the bell and the margin. Below this groove is a deeply scalloped bell margin with lap pets and tentacle-bearing organs. The mouth is on a short manubrium opening into a central stomach.
Little is known about their development, many members being known only from collections taken on deep-sea dredging expeditions. For instance, Atolla with a shallow, dark red bell is not usually found above 200 metres. Periphylla with a dome shaped, purple bell is common in deeper waters but is sometimes seen on the surface. Nausithoe and the small thimble-shaped Linuche inhabit shallow waters in the Bahamas and Florida region.
Sea wasps (Order Cubomedusae) These jellyfishes are unlike the other orders because the bells are cuboid with four flattened sides. They have a simple bell margin with groups of tentacles hanging from the four corners. Each tentacle consists of a wide portion near the bell and a narrower portion armed with nematocysts. The mouth at the centre of a short manubrium is deeply set in the subumbrella cavity and four septa divide the internal stomach region. They are found in open seas but are characteristic of tropical shallow waters, where they are powerful swimmers and feed on fishes. They are generally colourless and the best known is Charabdea with four single tentacles at the bell margin. All are noted for their powerful and often lethal sting and are feared by swimmers in coastal waters of south Japan, the Philippines and Australia, where they occur. Little is known about their life-history. Chiropsalmus quadrigatus is an example from northern Australian waters.
Stalked jellyfishes (Order Stauromedusae) Unlike the other members of the Scyphozoa, these jellyfishes are sessile and live fastened to seaweeds or stone by the exumbrella surface, feeding on small crustaceans. The bell is trumpet-shaped with a flattened subumbrella surface bearing tentacles and with a central mouth. The short, stalk-like body is anchored by an adhesive disc which in some cases is detachable, allowing the animal to move. They never swim but live in bays, sounds and coastal waters, generally in colder areas. Typically the margin of the bell is drawn out into eight lobes or four bifurcated lobes, each with a bundle of short tentacles at the tips. In between these lobes there may be dark patches representing adhesive organs.
Internally, stauromedusae resemble scyphis tomae, having an enteron divided by four septa. Typical planulae are produced which settle down and may bud off more larvae before growing into stalked, trumpet-shaped adults. Generally greenish or rose-pink in colour, they may measure several centimetres in diameter. The commonest genera are Haliclystus with eight dark patches and Lucernaria which has none. Whether this is a jellyfish which has become sessile, a scyphistoma which has become sexually mature, or an early member of the Cnidaria is a question which has not yet been settled by zoologists.