Dinner Plate Jelly (Solmissus sp.)
The Dinner Plate Jelly belongs to the Genus Solmissus, and derives its common name from its flat-shaped bell. Translucent white in color, they often are seen swimming with their long, string-like tentacles pointing upward. They are known for actively hunting their prey, which is generally gelatinous organisms such as ctenophores and other jellyfish. Dinner Plate Jellies are a common sight in the deeper waters above Axial Seamount and Slope Base. They can grow to be 20 cm (8 in) in diameter.
References:
Marine Life Field Guide (Neptune Canada)
http://jellieszone.com/hydromedusae/
http://www.imbc.gr/biblio_serv/deepsea/X4-0007.html
http://emeralddiving.com/id_jellyfish.html