Polymastia Sponge

Polymastia Sponge

Observation - Polymastia Sponge - UK and Ireland. Description: The body of this sponge is orange to yellow in colour and the papillae are pale yellow. The sponge consists of a low, spreading cushion (up to 1 cm thick), with papillae projecting above the sediment covered body. The papillae are differentiated into inh

"The body of this sponge is orange to yellow in colour and the papillae are pale yellow. The sponge consists of a low, spreading cushion (up to 1 cm thick), with papillae projecting above the sediment covered body. The papillae are differentiated into inhalant and exhalant; the exhalant papillae are large, few in number and open at one end, and can be easily distinguished from the thinner inhalant papillae." EoL
Never can we be certain with these things but http://species-identification.org/species.php?species_group=sponges&id=380 says it all for me. There are no absolute lookalike pictures in my books nor, I can find, on the webthing. But the structure (particulatrly the near-transparent longitudinal network), pale colour, exhalent/inhalent diferences all point to one species.
Picture 4, of almost certainly Polymastia betaformis (I am authoritatively told), is placed for comparison and is from the same site.
Both examples were growing in shallow, fine but gritty, sediment. P.bettaformis was down facing.
CORE EDIT - added annotations see comments