Yellow Scroll coral
Turbinaria sp. - Turbinaria reniformis more than likely - isn't the first coral you think of when adding livestock to your aquarium, but once you see some in another tank you realize you've been missing out far too long! The Yellow Scroll coral will grow in layers, forming cups and ripples as it matures in your reef.
Read the story about this coral here: http://www.reefaddicts.com/entry.php/29055-Yellow-Scroll-coral-over-time