Seaweed
"Seaweed" is a colloquial term and lacks a formal definition. A seaweed may belong to one of several groups of multicellular algae: the red algae, green algae, and brown algae. As these three groups do not have a common multicellular ancestor, the seaweed are in a polyphyletic group. In addition, some tuft-forming bluegreen algae (Cyanobacteria) are sometimes considered to be seaweed.
Endocladia muricata
"E. muricata" is common north of Point Conception, and is one of the most common algae in the high intertidal zone of the central California, coast. It commonly forms the top-most conspicuous band of seaweed along that coast. "E. muricata" often grows with "Pelvetiopsis limitata" (dwarf rockweed) and "Mastocarpus papillatus" (Turkish washcloth), on rocks in the high intertidal.
"E. muricata"'s thallus is 4–8 cm tall, short & bushy; branches cylindrical with sub-dichotomous branching; covered with minute, soft conical spines; blackish-brown to dark red to yellow. Dries to almost black. It is usually not slippery to walk on, dry or wet.