Mastocarpus pacificus

Thallus cartilaginous, 3-7(-13) cm high, dark reddish-brown, violet-carmine fading to yellowish-greenish color. Branching closely dichotomous, digitate. Branches narrowly to widely cuneate 1.5-5(-15) mm broad. Margins (rarely surface) papillate bearing cystocarps, 1-2 mm broad. Holdfast small, giving rise to erect axes. Growing in the lower intertidal zone, in intertidal pools on rocks (commonly in crevices), on stony bottom of exposed shores, often forming dense carpets or growing in association with other species (Laurencia nipponica, Chondrus yendoi).

North America (Alaska), Asia: Taiwan, Japan, Russia (Bering and Okhotsk Seas, the Sea of Japan).