the patterns of certain seashells are generated by natural cellular automata. examples can be seen in the genera "conus" and "cymbiola". the pigment cells are in a narrow band along the shell's lip. each cell secretes pigments according to the activating and inhibiting activity of its neighbor pigment cells, obeying a natural version of a mathematical rule. the cell band leaves the colored pattern on the shell as it grows slowly. for example, the widespread species "conus textile" bears a pattern resembling wolfram's rule 30 cellular automaton.