Tectura scutum (plate limpet)

Found in area 6 to 7

If the shell is round and looks like a checkerboard, it’s probably Tectura scutum, the plate limpet. They are hard to find because they are so flat and usually they are covered with mud so they look more like the rocks they are on than limpets. The clue is the round shape since that shape is not very common on the beach.