Here's a zoomed out view:
If it looks familiar, I showed a similar animal, but a different species, earlier this month.
This is the phoronid Phoronopsis harmeri (formerly Phoronopsis viridis). Note the long tentacles and the greenish coloration. This species lives on the tidal flats in Bodega Harbor. It's amazing to me that you can just park on the side of the road, walk out onto the mudflats, and find these beautiful animals in shallow pools. (There are only 14 species of phoronids in the world!)
The close-up photo above highlights an interesting feature of phoronids. Can you see the red color in some of the tentacles? Phoronids pump blood (containing hemoglobin) into their tentacles to absorb oxygen from the water, then move the oxygenated blood down into their body below the surface of the mud.
Several years ago, Eric wrote an excellent description of blood circulation in phoronids, accompanied by a very helpful illustration. I highly recommend reading his post called "Ebb and Flow."
Then return to this post and check out some of my favorite phoronid images from 25 July 2017:
Perhaps I'll try to get some video of the blood flowing up and down in the tentacles. Not sure whether my camera can capture that, but I think it's worth a try!