prostalia

from The Century Dictionary.

• In the morphology of the sponge-skeleton, those spicules of the Hexactinellidæ which project from the surface of the sponge-body. They comprise, according to position, prostalia basalia, which form the root tufts; prostalia marginalia, which form a circlet about the osculum; and prostalia pleuralia, which project from the lateral walls of the body.