Scientific name: Megabalanus californicus
Taxonomy: Kingdom Animalia → Phylum Arthropoda → Subphylum Crustacea → Superclass Multicrustacea → Class Thecostraca → Subclass Cirripedia → Infraclass Thoracica → Superorder Thoracicalcarea → Order Balanomorpha → Superfamily Balanoidea → Family Balanidae → Subfamily Megabalaninae → Genus Megabalanus
Locations: Eastern Pacific
Group: Marine Life → Invertebrates → Barnacles
California barnacles can grow to 2" - the same size as either snail full-grown. I'm not sure what'll happen when the barnacles outgrow their snails.