To _Caranx_, _Carangus_, and a number of related genera, characterized by the bony armature on the narrow caudal peduncle, a host of species may be referred. These fishes, known as cavallas, hard-tails, jacks, etc., are broad-bodied, silvery or metallic black in color, and are found in all warm seas. They usually move from the tropics northward in the fall in search of food and are especially abundant on our Atlantic coast, in Polynesia, and in Japan. About the Oceanic Islands they are resident, these being their chosen spawning-grounds. In Hawaii and Samoa they form a large part of the food-supply, the ulua (_Carangus forsteri_) and the malauli (_Carangus melampygus_) being among the most valuable food-fishes, large in size and excellent in flesh, unsurpassed in fish chowders. Of the American species _Carangus chrysos_, called yellow mackerel, is the most abundant, ranging from Cape Cod southward. This is an elongate species of moderate size. The cavalla, or jiguagua, _Carangus hippos_, known by the black spot on the opercle, with another on the pectoral fin, is a widely distributed species and one of the largest of the tribe. Another important food-fish is the horse-eye-jack, or jurel, _Carangus latus_, which is very similar to the species called ulua in the Pacific. The black jack, or tiñosa, of Cuba, _Carangus funebris_, is said to be often poisonous. This is a very large species, black in color, the sale of which has been long forbidden in the markets of Havana. The young of different species of _Carangus_ are often found taking refuge under the disk of jelly-fishes protected by the stinging feelers. The species of the genus _Carangus_ have well-developed teeth. In the restricted genus of _Caranx_ proper, the jaws are toothless. _Caranx speciosus_, golden with dark cross-bands, is a large food-fish of the Pacific. _Citula armata_ is another widely distributed species, with some of the dorsal rays produced in long filaments. In _Alectis ciliaris_, the cobbler-fish, or threadfish, the armature of the tail is very slight and each fin has some of its rays drawn out into long threads. In the young these are very much longer than the body, but with age they wear off and grow shorter, while the body becomes more elongate. In _Vomer_, _Selene_, and _Chloroscombrus_ the bony armature of the tail, feeble in _Alectis_, by degrees entirely disappears.