Tentorium Vosmaer, 1887

Diagnosis: Polymastiidae with columnar or globular growth form protected by a dense cylindrical sheath of longitudinally placed spicules which form a solid imperforate layer. The ectosomal skeleton contains bundles of smaller spicules arranged in a palisade and is limited to the upper surface of the cylinder. Ostia are present on the upper surface. The oscule at the top of a small papilla is on centre of the upper surface. Megascleres are subtylostyles and tylostyles (Boury-Esnault 2002).