The polyp sits in a calcareous cup, the corallite. It is resistant to predation as it has well-developed radial corallite lips. Rugose corals always show tabulae, horizontal plates that divide the corallite skeleton. The inner surface of the corallite is known as the calyx. Extratentacular budding always results in separate polyps, each with its own corallite wall. The polyp can almost completely retract into its stony corallite cup. The skeleton of an individual scleractinian polyp is known as a corallite. Coenosteum and corallite walls are porous, which can result in elaborate structures. Where there is no corallite wall, the blades are known as septocostae. The corallite is vase-shaped and has a short pedestal.