Ralfsia pacifica (Hollenberg)
Description: This plant forms a flat encrusting layer, firmly attached to the substrate; it is irregularly circular in outline, often lobed at the margin, 2-12 cm. in diameter, 0.5-1.0 cm. thick, and olive brown to black in colour; surface with radial or concentric rings.
Habitat: On rocks and shells in the middle and lower intertidal zones.
Pacific Coast Distribution: Alaska to Mexico.
Robert Scagel, 1972