It is the exoskeleton of a crab. The mystery photo is a view of the crab's legs. This exoskeleton was left by a crab after it molted. We think it was from a dungeness crab. As they grow, crabs need bigger shells. They can molt up to 15 times in their life.
Clue #1 This was "armor" for a creature in the ocean.
Clue #2 It has eight legs plus two claws.
Clue #3 It was found on a beach.