- Kingdom: Animalia
- Phylum: Cnidaria
- Class: Hydrozoa
- Subclass: Hydroidolina
- Order: Leptothecata
- Family: Tiarannidae
- Scientific name: Modeeria rotunda
- Norwegian: -
Hydroid stage: The typical height of the hydroid is less than 2 mm, so it will probably not get much attention from scuba divers.
Medusa stage: The transparent, hemispherical bell may reach a diameter of 22 mm. Vivid orange gonads are attached to four radial canals. Along the narrow ring canal there are 16-30 tentacles.
The medusae is regarded as a deep water species, but the individual on the images was seen just below the surface. The hydroid is usually found on other colonial hydroids. There are registrations as deep as 680 meters.
We do not know too much about the distribution. It has been collected in the North Atlantic, Mediterranean Sea, Pacific Ocean and of Antartica.