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The Mackerels

Body elongate, fusiform, not much compressed, covered with minute, cycloid scales, those anteriorly forming a corselet; lateral line undulate; head subconic, pointed anteriorly; mouth rather large, premaxillaries not protractile; no supplemental maxillary bone; jaws with sharp teeth; preopercle entire; opercle unarmed; gill-openings very wide, the membranes not united, free from the isthmus; pseudobranchiae large; branchiostegals 7; dorsal fins 2, the first of rather weak spines, depressible in a groove, the second similar to the anal, the elevated anterior lobe always distinct; anal spines weak; last rays of dorsal and anal detached and separate, forming in each case a series of finlets; caudal peduncle extremely slender, keeled, the caudal lobes abruptly divergent and falcate, the fin adapted for rapid motion; ventral fins 1, 5, thoracic and well developed; lower pharyngeals separate; stomach sac-shaped; pyloric coeca numerous; air-bladder small, sometimes absent. Colouration, metallic, often brilliant, the prevailing shade steel-blue.