The word Actinopterygii is formed from the Greek word actis meaning rays, pteryx meaning fin. Actinopterygii means ray-finned. Ray-finned fishes are known as Actinopterygii. About 96% of living fish belong to this category. They are 10 mm to 4 m long and weigh 1500 kg. Their number of species is 31,045. 12 classes, 48 tribes and 253 species of this class have been identified in the fresh water of Bangladesh.