- Kingdom: Animalia
- Phylum: Porifera
- Class: Calcarea
- Order: Leucosolenida
- Family: Sycettidae
- Scientific name: Sycon quadrangulatum
- Norwegian: urnekalksvamp
Because of the shape and the single opening (oscule) at the end of the cylinder, it can be confused with a sea squirt on some distance. The opening is framed by fine hairs. The color is white, grey or light brown. It can reach a length of 9 cm after a life span usually no more than one year. Larvae are released in the spring and the sponge often dies immediately after.
S. quadrangulatum seems to prefer shallow waters, where it can be found attached to rocks or algae.
Common along the Atlantic coast of Europe, from the Mediterranean to the coast of Norway.