- Meaning "Box Jellyfish".
- These animals used to be grouped with the Scyphozoas but recently they have been separated because of increasing numbers that have been found.
- Today there are about 20 species known.
- They range in size from 2 to 25 cm.
- They are also the only Cnidarian with a complete nerve-ring.
- They also have four evenly spaced out tentacles or bunches of tentacles and well-developed eyes.