The opossum fish is a class of bony fish in the order Scleractinia, family Plaiceidae, which is a class of flounder. The body of the opium fish is laterally compressed, asymmetrical, both eyes are on the left side; mouth anterior position, the lower jaw has a protruding; the edge of the anterior gill cover bone is free; the skin on the side of the eye is dark gray or patchy lines, the skin on the side of the eye is not white. Opium fish is mainly used as fresh food or made into canned and salted dried products, the liver can be extracted to make cod liver oil. Opium fish in the flounder species is China's Yellow Sea and the Bohai Sea valuable fish, and other varieties of flounder is the same season to welcome when the flavor of the famous dishes, do out of the dishes bright colors, spicy and fat. Turbot species, widely distributed in the tropical or temperate zones of the ocean, China's coastal areas are also produced. According to the rules of classification of left flounder and right plaice, opium fish is a kind of plaice, and it is wrong to say that opium fish is an alias of flounder. The scientific name of the opium fish is Greenland flounder.