Chambered nautilus – Nautilus pompilius.The exquisite, multi-chambered shell of the nautilus serves as its protection as well as its flotation devise. It fills its shell with water when it wants to sink, dispels water to rise, and moves laterally through jet propulsion. The nautilus is a “living fossil” – an ancient animal that dates back more than 400 million years and still makes its home in deep water. ..The nautilus shell is a logarithmic or equiangular spiral. Such a shape arises because a growing animal has the same proportions as it grows and the spiral fits the requirement to protect this shape as it gets larger. This shell embodies what the ancient Greeks termed as a “Golden Rectangle”.