Age : Jurassique , Callovien Provenance : Jar-Sur-Mer , France 14 cm Well displayed on a thick metal support. The specimen is very heavy . These nautiloids are much rarer than the ammonites so frequently seen. A nautilus's shell is made up of two layers. The inner layer has the iridescent shine, while the outer layer provides protection from external forces. Inside the shell are septa that divide the living area of the shell into compartments and help the animal maintain balance and position in the water column. Nautilus are "living fossils": species similar to this one still exist in our oceans! The nautilus is a free-swimming mollusk related to the squid or octopus, but with a hard, multi-chambered spiraling shell.