Cellular automaton
The patterns of certain seashells are made by natural cellular automata. Examples can be seen in the genera Conus and Cymbiola. The pigment cells are in a narrow band on the shell's lip. Each cell secretes pigments based on what pigment cells around it are doing. The cell band leaves the colored pattern on the shell as it slowly grows. For example, the species Conus textile has a pattern that looks similar to Wolfram's rule 30 cellular automaton.