Two or 3 (?) latticed shells, outermost with characteristically sub-quadrangular outline, moderately thick-walled, thorny, with irregularly shaped pores; medullary shell spherical. Six stout beams join the two shells; usually two of these beams protrude outside as short, 3-bladed polar spines, but the other two pairs may also extend slightly beyond the cortical shell-wall. Polar spines of equal or different size. Outermost shell diameter without spines: 80-130 µm.
Ref.: Benson (1966).