A comprehensive group equivalent to the true Cœlenterata, i. e., exclusive of the sponges. They are so named from presence of stinging cells (cnidae) in the tissues. See Coelenterata.

Phylum which includes very primitive, carnivorous animals with stinging tentacles. Cnidarians may appear as a sessile polyp (as seen in hydroids and sea anemones) or as a floating medusa (as characterized by jellyfish). Anyone who has ever been swimming in the Chesapeake Bay is familiar with the phylum Cnidaria because of the abundance of of sea nettles in the summer months. The Chesapeake Bay is also home to many other cnidarians, including beautiful sea anemones.

A phylum comprising four taxonomic classes: Hydrozoa (hydroids), Cubozoa (sea wasps and box jellies), Scyphozoa (jellyfish), and Anthozoa (corals and sea anemones). Hydroids are considered the most primitive of the four classes; the other three classes probably evolved from hydroids. Scyphozoa spend most of their lives in the medusa stage, while Anthozoa spend most of their lives as polyps.

phylum of aquatic invertebrates (formerly called Coelenterata) that includes Hydra, jellyfish, sea anemones, and corals. These animals have stinging cells on their tentacles and can occur in different body forms. They may be free-swimming medusa and/or attached polyps hydroids).