Again, under a dock at Pillar Point Harbor. It matches the description of Myxicola infundibulum in Light's in that it has violet radiolar tips, but I'm not sure you would call a dock a "soft sediment."
Anyone know it? I think the whole colony might have been 10-15 cm across. That's a large mussel in the left of the image, if that helps with scale.
Update: Polychaete expert leslieworms from Flickr gave me a really great description of the taxonomic situation of Myxicola in CA.
