Cellaria fistulosa is an erect bryozoan, composed of jointed dichotomous branches. The colonies form large white clumps, which grow 5-6 cm in height or more. The colonies often grow bigger than other Cellaria species, and branch frequently to form an extensive diffuse growth. The internodes narrow proximally (towards the colony origin), but they are not club-shaped as with C. sinuosa. Cellaria fistulosa is a more slender species than C. sinuosa, with a smaller internode length and diameter (commonly 0.4-0.8 mm). Colonies are anchored to the substrate via chitinous rootlets.
Autozooids are generally hexagonal, but pointed at the tip. The are arranged in a longitudinal series, each autozooid being in contact with those directly above and below it.
Differentiating between Cellaria species is difficult and C. sinuosa is frequently mistaken for C. fistulosa
Cellaria fistulosa is widely distributed
in warm and temperate sea. It is found in waters off all British coasts
The species is able to colonise stones and shells in subtidal waters.
Its depth range is uncertain, but it is known to occur at depth of 30-80
metres in the Mediterranean.