Angel Ledge, Midway Atoll, 80 feet

Fission, Pearl & Hermes Reef, 50 feet

Haleiwa Trench, Oahu, 60 feet

Kewalo Pipe, Oahu, 50 feet

Uncommon on reefs at scuba depths.  Circular with central hump, ribs of uniform height, bottom concave.  Easily confused with the smaller Cycloseris vaughani.  Attains 4 inches.  Hawaii & the Indo-Pacific.

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