A plane tiling is said to be isohedral if the symmetry group of the tiling acts transitively on the tiles, and -isohedral
if the tiles fall into n orbits under the action of the symmetry group of the tiling.
tiling is a tiling which permits no -isohedral tiling with
The numbers of anisohedral polyominoes with , 9, 10, ... are 1, 9, 44, 108, 222, ... (OEIS A075206),
the first few of which are illustrated above (Myers).