Sharkfin, Lana'i, 80 feet

Pearl & Hermes Reef, NWHI, 35 feet

Sharkfin, Lana'i, 80 feet

Kewalo Pipe, Oahu, 55 feet

Makua, Oahu, 25 feet

Beachworn specimens

Uncommon on sand or rubble in deeper water.  Circular & domed with six prominent ribs, bottom slightly convex at the center.  Yellow-brown, sometimes fluorescent orange or green.  Juveniles are hexagonal and formerly called Cycloseris hexagonalis.  Attains 1.5 inch.  Red Sea to Hawaii and French Polynesia. 

All coral skeletons illustrated are from scientific collections taken prior to 1998.