Form: Thin sheet or cushion covering rock in patches to 15cm or more in diameter.

Colour: Red to reddish-orange.

Smell: ?

Consistency: Crumbly.

Surface: Bumpy-rough. Excurrent channels may be obvious.

Apertures:

• The oscules are fairly regularly distributed and reasonably obvious because of the presence of converging channels.

Contraction:

• Some, especially of the oscules.

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Synonyms: Referred to as Microciona sp. 'A' in a previous edition of this guide.

Internal characters

Skeleton: Typical Microciona with plumose columns of large, nearly smooth, acanthostyles echinated by smaller, entirely-spined acanthostyles. There is a surface layer of subtylostyles and very abundant minute chelae. Toxa may be rare and not present in all specimens. Fine flexuous subtylostyles may be common, scattered throughout the tissue.

Spicules: Spiculation is similar to that of Microciona spinarcus. The toxa taper to points and are sparsely spined near their ends.

Identity: This sponge is very similar to M. spinarcus (q.v.). The presence of flexuous subtylostyles and scarce microspined toxa seems to be characteristic. This, combined with the bumpy surface, may be diagnostic.

Distribution Map from NBN: Microciona fallax at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Microciona fallax at iNaturalist World Species Observations database.

WoRMS: Microciona fallax at World Register of Marine Species. Accepted name: Clathria (Microciona) fallax (Bowerbank, 1866). AphiaID: 167638.

Classification: Biota; Animalia; Porifera; Demospongiae; Heteroscleromorpha; Poecilosclerida; Microcionidae; Microcioninae; Microciona

Voucher: BELUM : Mc1763. Calf, Isle of Man.

Editors: D. Moss, B.E. Picton.