Blowhole, Oahu, 20 feet

Kahe Point, Oahu, 20 feet

Common on vertical surfaces exposed to current or surge.  Inner margin is purple with brown ribs.  Pearlfish take shelter within the mantle cavity.  Attains 6 inches.  Hawaii & the Indo-Pacific.  Spondylus tenebrosus and Spondylus violacescens are synonyms.