Noumea haliclona from Victoria, Australia

Dear Trevor,
Yes this is one of the colour forms of Noumea haliclona.  The 'protuberance' along each side is just a flod of the mantle edge. Quite a few species of Noumea do this and in some species, such as N. decussata, it is a characteristic of the species. One common colour character found in all the colour forms of N. haliclona is the red or orange spot just below the tip on the front of each rhinophore.

This species use feeds on pink or yellow species of darwinellid sponge. In your photo, the orange-brown sponge in the lower right corner looks like a darwinellid, so it is possible that that is its food sponge as well, so it would be worth keeping an eye out for it on such a sponge.

Best wishes,
Bill Rudman