@stc
Biological Pigmentation Patterns
"In each close-up the pattern grows from top to bottom, just like in a one-dimensional cellular automaton. Patterns with triangles are often said to have a "tent" or "divaricate" form. The shell on the bottom right is a slightly rare specimen where something close to an explicit nested pattern can be seen. Most of the shells are between one and four inches long; the one on the bottom right is nine inches long.
The patterns are all various shades of brown on roughly white backgrounds. The shells are the following types: first row: Elliot's volute, vexillate volute, lettered cone; second row: music volute, banded marble cone, tent olive; third row: bough cone, textile cone, false melon volute (Livonia mammilla)."
in: Stephen Wolfram - A New Kind of Science (p 423)