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USA: California: San Diego County: .Still life of a Pearl Nautilus shell (in a blue cast of lighting) - Pearl nautilus are the end result of the removal of the brown and white exterior of the shell.  This reveals the beautiful pearl that lies beneath. In Polynesia this shell is believed to have the ability to chase away evil spirits. Nautilus are Cephalopods in a group including the squid, octopus and cuttlefish. Cephalopods are the most highly evolved mollusks.  They have a well developed nervous system and highly developed eyes. Surrounding the mouth are many tentacles.  The Nautilus are the only cephalopod to have a true external shell.  Naturalists, mathematicians and physicists have been fascinated for years by the form of this shell. The spirally coiled, chambered shell is perfectly proportioned mathematically- a remarkable feat of natural engineering.  The shell has several gas filled chambers that serve as a balancing apparatus. The nautilus is considered a living fossil.  It has been traced back 500 million years. .(6x8cm)