This sponge can be very polymorphic, varying from a cushion to almost a branching-repent form. A cushion can give rise to oscular chimneys with oscules at the top or, more typically, to a profusion of simple, solid, tassel-like branches with the oscules mainly along their length (cf. Halichondria panicea
). In some sheltered localities the branches grow over other organisms and loop like bramble stolons, attaching to any suitable object they encounter. The colour is usually buff or cream, never green. The variable nature of Halichondria bowerbanki
can make it very difficult to identify positively. The most likely confusion is with Halichondria panicea
. The growth of tassels in H. bowerbanki
seems to be a good character, but these are not present all year round. H. bowerbanki
lacks the green colour that is present in H. panicea
in well lit conditions and also the characteristic smell.