The wall is a raised skeletal structure surrounding the corallite. It separates neighbouring corallites, and internal structures from the surrounding colony surface.
The wall is a skeletal structure surrounding and defining the corallite.
The corallite is the skeleton home built by the coral polyp. At its simplest the corallite structure can be described using three terms - wall, septa and costae.
Many genera, such as Favia (p.10 of the Coral Finder) have distinct walls but sometimes corals may be described as possessing ‘indistinct walls’. The corallites of these genera are not separated by a clear cut wall structure. Pavona (p. 12 of the Coral Finder) is one genus with indistinct walls.
(Picture from glossary, photo of favia and pavona)
Many corals show distinct walls to their corallites. Presence, absence and type of wall is important for defining coral genera (singular genus).
Some corals have absent or indistinct walls - the genus Pavona.
Ridges vs. walls. In this Oulophyllia the corallites are forming a system of valleys and ridges. In this case the ridge is also a corallite wall.