Onustus caribaeus is a species of large sea snail, a marine gastropod mollusk in the family Xenophoridae, the carrier shells.

Their shells have a flat bottom and a short conical spiral on top.

[2] They are known for their ability to camouflage by attaching substrates like pebbles, sand, empty shells, and even coral to the top of their shells.

[6] Like other snails, O. Caribaeus have a radula, used for scraping detritus and other substances off of substrates to feed on, and a muscular foot used for locomotion.

[7] Onustus caribaeus is distributed in the North-eastern Gulf of Mexico, the Caribbean Sea and along the Atlantic coast of Brazil between 35m and 640m (mostly deeper than 100m).