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.