Nautilus belauensis

Nautilus belauensis, also known as the Palau nautilus, is a species of nautilus native to the waters around the Pacific island nation of Palau. N. 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 N. pompilius pompilius. The shell is usually up to around 210 mm in diameter, although specimens up to 226 mm have been recorded.