California mussel; shell bluish-black, heavy; anterior end pointed, posterior rounded; prominent radial ribs (often eroded). Attached with tough, proteinaceous byssal threads. Filter feeder.
Very abundant, exposed outer coast, forms multilayer beds in upper-mid intertidal zone. Dominant space competitor, preyed on by sea stars (Pisaster ochraceus), sea otters, whelks, crabs & birds.Geogr. Range: Aleutian Islands, Alaska to Baja