 Above the mouth is the epistome, a hollow lid which can close the mouth.The cavity in the epistome is sometimes called the protocoelom, although other authors disagree that it is a coelom and Ruppert, Fox and Barnes think it is built by a different process.When the lophophore is extended, cilia (little hairs) on the sides of the tentacles draw water down between the tentacles and out at the base of the lophophore.