I think this is Rockweed ... a species of brown alga in the family Fucaceae to be found in the intertidal zones of rocky seashores in the Northern Hemisphere.
Lots and lots of feather boa this time. Didn't collect any. This and nori seemed to dominate.
This is Pterygophora californica (Old Growth Kelp), about 4' long.
You can find fresh Nereocystis luetkeana (Bull Kelp) on the beach these days, or examples like these, slightly dried out already.
The Alaria marginata (Broad-winged Kelp) looks prettiest when sand fills its grooves.
Another very common seaweed at North Beach: Fucus gardneri (Rockweed).
This Egregia menziesii (Feather Boa Kelp) is one of the most common seaweeds this time of year at North Beach.
This Desmaresti viridis (Stringy Acid Weed) is frequently washed up on our beach.
This Laminaria bongardiana (Split Kelp) is quite large and an interesting find.