Orange Sponge

It's always good to come across a new species, as we did on the rocks at Sanna yesterday, but often something like this is difficult to identify. For once, it was relatively easily found on Google, though an initial search for 'orange algae' proved fruitless.

This is Hymeniacidon perlevis, or something very similar. It's a sponge which is found in the intertidal zone and is not uncommon around Britain's coastline - more here.