The chambered nautilus, also called the pearly nautilus, is the best-known species of nautilus. The shell, when cut away, reveals a lining of lustrous nacre and displays a nearly perfect equiangular spiral, although it is not a golden spiral. The shell exhibits countershading, being light on the bottom and dark on top. This is to help avoid predators, because when seen from above, it blends in with the darkness of the sea, and when seen from below, it blends in with the light coming from above.
Chambered nautilus
The first and so far oldest known fossil of chambered nautilus, displayed at the Philippine National Museum.
1896 skiagraph (X-ray photograph) of a N. pompilius by James Green & James H. Gardiner, from Proceedings of the Malacological Society of London, Vol. II, Pl. XV, p. 178
16th-century Northern Mannerist nautilus cup
The nautilus is an ancient pelagic marine mollusc of the cephalopod family Nautilidae. The nautilus is the sole extant family of the superfamily Nautilaceae and the suborder Nautilina.
Nautilus
The first and oldest fossil of chambered nautilus displayed at Philippine National Museum.
Nautilus half-shell showing the camerae in a logarithmic spiral
Section cut of a nautilus shell
