In the coves and crevices at Natural Bridges State Park, Santa Cruz, California, one can find large masses of worm tubes constructed of sand. These tube masses often cover areas of several square feet. The tubes are usually straight and packed together in large masses. The individual tubes are about one-fourth of an inch in diameter and may be up to two and one-half feet long. The worm responsible for these masses of tubes is a small polychaete, Phragmatopoma californica. Very little work has been done on the natural history of local sabellarlids. It is therefore the purpose of this paper to present data pertaining to the natural history of the sabellarlid polychaete, Phragmatopoma california. Such data will include notes of the reproduction, feeding, tube building habits, and associated biota of this polychaete as well as a description of its digestive system.