-The purple sea urchin Strongylocentrotus purpuratus digests the brown algaeMacrocytis pyrifera and Egregia Laevigata with high efficiency, averaging 80 per cent digested for the former and 62 per cent for the latter. The brown algae Petalonia fascia and Halidrys dioica are not the usual diet of this animal and are digested with lower efficiencies, 50 and 44 percent respectively.