The steep-sided shell is formed of six plates finely striped vertically with reddish-purple and white.

The mantle, visible through the wide aperture, is margined with red, orange, yellow and blue.

This barnacle could be confused with Megabalanus coccopoma, but that species is paler, has a smaller aperture and narrower radii between the plates.

[2][3] Megabalanus californicus occurs in the Eastern Pacific Ocean in the subtidal and intertidal zones of rocky shores.

After six stages these develop into zoea larvae which settle on the seabed, cement themselves to the substrate and undergo metamorphosis into juveniles.