Sesimbra, Nautilus.
Nautilus (in vernacular Portuguese, nautilus) is a genus of marine nektonic cephalopod molluscs from the Indo-Pacific, classified by Carolus Linnaeus, in 1758, in his Systema Naturae, when describing its best-known species: Nautilus pompilius. They belong to the family Nautilidae and order Nautilida,characterized by having a large calcareous external shell with a convoluted spiral (brevicone type), divided into chambershragmocone) which are pierced by a siphon and used as a protection and flotation device. Their buoyancy is controlled by the animal by pumping liquid or gas in and out of these chambers, through osmosis;providing them with vertical movements,while their horizontal movements are provided by water jets , expelled through funnel tubes, visible between the two lowest tentacles, propelling them forward or backward.