Branchioplax washingtoniana Crab, from Hoko Formation, Clallam County, Washington State, U.S.A. (REF:BRCAB2)

Branchioplax is an extinct genus of crab which existed in Alaska and Washington during the Eocene period. 

Named by Mary Rathbun (an American zoologist who specialized in crustaceans) in 1916, and contains ten species, including Branchioplax washingtoniana from the Hoko River Formation.