The Palau Nautilus (Nautilus belauensis) is a species of nautilus native to the waters around the Pacific island nation of Palau. Nautilus belauensis is very similar to Nautilus pompilius and shares with this species a closed umbilicus covered with a callus. It differs on the basis of a modified radula and fine raised ridges across and along the shell, which form a cross-grid texture. N. belauensis is the second largest nautilus after the giant form of Nautilus pompilius pompilius. The shell is usually up to around 210 mm in diameter, although specimens up to 226 mm have been recorded.