Semaeostomeae

Semaeostomeae (literally "flag mouths") is an order of large jellyfish characterized by four long, frilly oral arms flanking their quadrate mouths. The umbrella is domed with scalloped margins, and the gastrovascular system consists of four unbranched pouches radiating outwards from the central stomach; no ring canal is present. They usually possess eight tentacles; four are per-radical and four are inter-radical.

The Ulmaridae are a family of jellyfish, which includes the moon jellies, and other jellyfish with unique characteristics like Tiburonia granrojo.

The Pelagiidae are a family of jellyfish. Members of the family Pelagiidae have no ring canal, and the marginal tentacles arise from umbrella margin.

The Cyaneidae are a family of true jellyfish. About 20 species are in this family, including the well-known lion's-mane jellyfish.

Phacellophora, commonly known as the fried egg jellyfish or egg-yolk jellyfish, is a very large jellyfish in the monotypic family Phacellophoridae containing a single species Phacellophora camtschatica. This genus can be easily identified by the yellow coloration in the center of its body which closely resembles an egg yolk, hence its common name. Some individuals can have a bell close to 60 cm (2 ft) in diameter, and most individuals have 16 clusters of up to a few dozen tentacles, each up to 6 m (20 ft) long. A smaller jellyfish, Cotylorhiza tuberculata, typically found i