Urticina crassicornis, painted or Christmas anemone
"A non-selective and opportunistic predator, Urticina crassicornis, may feed on crabs, sea urchins, mussels, gastropods, chitons, barnacles, fish, and sometimes sea stars and stranded jellies." (Wikipedia)This was a medium-sized one; about two inches across. They grow to about three inches, with the open tentacles reaching to 10 inches across. They can live up to 80 years.