Morphology:
Colony is encrusting, forming irregular patches or cylindrical incrustations around erect hydroids. The autozooids grow as a single layer. Autozooids are very distinctive having a long projecting peristome. This gives colonies a characteristic spiky appearance.
Size:
Autozooids are 0.6-0.8x0.4-0.5 mm. They are separated by distinct grooves.
Distribution:
British records include Northumberland, Orkney, the Clyde Sea, the Isle of Man and the southern Irish Sea.
Habitat:
This species is rarely found on the lower shore and is typically sublittoral. It can grow on large solitary Ascidians such as Ascidia mentula, decapods shells and shell valves.
Taxonomic name: