- Kingdom: Animalia
- Phylum: Chordata
- Subphylum: Tunicata
- Class: Ascidiacea
- Order: Phlebobranchia
- Family: Corellidae
- Scientific name: Corella parallelogramma
- Norwegian: parallellogram-sekkedyr
The gas mantle ascidian is easily identified, due by the grid of water channels, forming a large number of small parallelograms. These are clearly visible through the transparent body wall. This grid is usually white, but sometimes it takes other colors, probably due to substances extracted from the filtered water. If you look closely, you can see some small orange spots around the siphons. The body may grow to a height of 5 cm and a width of 3 cm. The mouth siphon and the outlet siphon is placed close to the top. The white digestion channel and a small heart at the bottom are usually clearly visible.
It lives on hard substrate from the subtidal zone and down to a few hundred meters.
The registrations span from Norway to the Mediterranean.