Trichiurus.—Body band-like, tapering into a fine point, without caudal fin. One single dorsal extending the whole length of the back. Ventrals reduced to a pair of scales, or entirely absent. Anal fin rudimentary, with numerous extremely short spines, scarcely projecting beyond the skin. Long fangs in the jaws; teeth on the palatine bones, none on the vomer.
The “Hairtails” belong to the tropical marine fauna, and although generally found in the vicinity of land, they wander frequently out to sea, perhaps merely because they follow some ocean-currents. Therefore they are not rarely found in the temperate zone, the common West Indian species (T. lepturus), for instance, on the coast of England. They attain to a length of about four feet. The number of their vertebræ is very large, as many as 160, and more. Six species are known.
Epinnula.—Body rather elongate, covered with minute scales,[*. see below] The first dorsal fin continuous, with spines of moderate strength, and extending on to the second; finlets none; ventrals well developed. Lateral lines two. Teeth of the jaws strong; palatine teeth, none.
The “Domine” of the Havannah, E. magistralis.
Thyrsites.—Body rather elongate, for the greater part naked. The first dorsal continuous, with the spines of moderate strength, and extending on to the second. From two to six finlets behind the dorsal and anal. Several strong teeth in the jaws; teeth on the palatine bones.
The species of this genus attain to a considerable size (from four to five feet), and are valuable food fishes; Th. atun from the Cape of Good Hope, South Australia, New Zealand, and Chili, is preserved, pickled or smoked. In New Zealand it is called “Barracuda” or “Snoek,” and exported from the colony into Mauritius and Batavia as a regular article of commerce, being worth over £17 a ton; Th. pretiosus, the “Escholar” of the Havannah, from the Mediterranean, the neighbouring parts of the Atlantic, and the West Indies; Th. prometheus from Madeira, Bermuda, St. Helena, and Polynesia; Th. solandri from Amboyna and Tasmania is probably the same as Th. prometheus.
Young specimens of this (or, perhaps, the following) genus have been described as Dicrotus. In them the finlets are not yet detached from the rest of the fin; and the ventral fins, which are entirely obsolete in the adult fish, are represented by a long crenulated spine.
Gempylus.—Body very elongate, scaleless. The first dorsal fin continuous, with thirty and more spines, and extending on to the second. Six finlets behind the dorsal and anal. Several strong teeth in the jaws, none on the palate.
One species (G. serpens), inhabiting considerable depths of the Atlantic and Pacific Oceans.