the name of a genus of shell-fish belonging to the order of vermes testacea. The shell consists of one spiral involuted valve. There are two species of argonauta, viz. The argo with a subflected carina, which is found in the Mediterranean and Indian oceans. This is the famous nautilus of other authors. It lies on the surface of the water, and extends an exceeding thin membrane, which it uses in some measure both as sails and oars; and in this manner it swims from one place to another. 2. The cymbium with a blunt plaited carina. This species is very small, and is found in the Mediterranean.