Acorn Barnacle

Scientific Name: Balanomorpha
Range: Aleutian Islands to Mexico
Habitat: Mid to high intertidal on wave-swept rocky shores.
Diet: Plankton
Size: 0.7 - 4 in (2-10 cm)
Fun Fact: Barnacles use modified legs called cirri to "catch" and strain plankton during high tide. 
IUCN Conservation Status: Not endangered