There are no repetitive numbers on each of the dodecahedra. All of these regular star dodecahedra have regular pentagonal or pentagrammic faces. With twelve faces, it is one of many nonregular dodecahedra. The two pyritohedra can be superimposed to give the compound of two dodecahedra. Other forms include dodecahedra and (rarely) cubes. A dodecahedron flake, or sierpinski dodecahedron, is formed by successive flakes of twenty regular dodecahedra. The image to the left shows the case where the pyritohedra are convex regular dodecahedra. The convex regular dodecahedron also has three stellations, all of which are regular star dodecahedra. The elongated dodecahedron and trapezo-rhombic dodecahedron variations, along with the rhombic dodecahedra, are space-filling. This 4-polytope has 14 polyhedral cells&colon; 2 dodecahedra connected by 12 pentagonal prisms. The dodecahedral prism consists of two dodecahedra connected to each other via 12 pentagonal prisms. Although regular dodecahedra do not exist in crystals, the tetartoid form does. The dodecahedra alone make a lattice of edge-to-edge pyritohedra. Regular dodecahedra have been used as dice and probably also as divinatory devices. Roman dodecahedra date from the 2nd to 4th centuries AD.