This Sunburst Anemone (or Starburst Anemone, Anthopleura sola) has its column encrusted with shell fragments and pebbles, and folds into a ball for protection and camouflage at low tide. Its pale green tentacles are barely visible along the inner ring. As additional self-defense, it contracts into a tighter ball upon contact with a large object.
https://en.wikipedia.org/wiki/Starbur...
Cabrillo National Monument tide pool, San Diego. Feb 10, 2024