What is the X in X-mas?
any of the thin, deep-bodied, more or less oval and silvery fishes of the family Stromateidae (order Perciformes). Butterfishes are found in warm and temperate seas and are characterized by a small mouth, forked tail, and a single dorsal fin. Like the related rudderfishes (Centrolophidae) and man-of-war fishes (Nomeidae), they also have peculiar, toothed outpocketings in the esophagus. (In some systems of classification Centrolophidae and Nomeidae are included in Stromateidae.)