Mollusca

Mollusca (Mollusca) is a general term for all species of Cephalopoda (Cephalopoda), there are about 650 species, all seafood, such as octopus, cuttlefish, nautilus, squid, etc. From near shore to far sea, from the surface to depths below 4,500 meters. 

Low-salinity water is rare. Baltic water has low salt content and no cephalopods, but the Suez Canal has them. There are more extinct species than existing species, peaking at the end of the Paleozoic and Mesozoic, the most well-known such as ammonites and arrow stones. Cephalopods and gastropods are closely related.