- Kingdom: Animalia
- Phylum: Chordata
- Subphylum: Tunicata
- Class: Ascidiacea
- Order: Aplousobranchia
- Family: Polyclinidae
- Scientific name: Synoicum pulmonaria
- Norwegian: -
This is a colonial sea squirt. The colonies often take a globular form. The diameter may exceed 10 cm, but smaller colonies around 2 cm seems to be much more common. The zooids are arranged in a regular system, where typically 6-8 inhalant openings surround a larger exhalant opening. Inside each zooid, up to 25 mm of length, there is a smooth stomach and a U-shaped gut. S. pulmonaria is semi transparent, yellowish grey. They are often, but not always, encrusted with sand.
It has been confused with S. incrustatum and Polyclinum aurantium. The former never forms such large colonies and is encrusted with sand. P. aurantium has a irregular arrangement of zooids around the cloacal openings.
It is often seen on hard substrate, preferably on moderately current-exposed locations, on depths from 15 meters and down to 600 meters.
It is mostly registered in the North Sea, including the coast of Norway and the Northern parts of the British Isles. It is believed to have a Arctic-Boreal distribution.