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"Acorn-shell (Balanus tintinnabulum). T., tergum; CR., thoracic legs; R., outer shell in section; D., aperture of oviduct; F., mantle cavity; X., depressor muscle of tergum; AN., antennae; OV., ovary; G., depressor of scutum; H., oviduct; AM., adductor muscle of scuta; S., scutum." -Thomson, 1916

Acorn Shell

"Acorn-shell (Balanus tintinnabulum). T., tergum; CR., thoracic legs; R., outer shell in section; D.,…

"Acorn barnacle, with arms extended." -Cooper, 1887

Acorn Barnacle

"Acorn barnacle, with arms extended." -Cooper, 1887