The body is naked, pectoral fins are usually absent, and the gill-cleft is a small round opening. The opercular bones are much reduced in size, and the pectoral arch may be totally absent.
Voracious marine Fishes, inhabiting tropical and subtropical waters, being especially abundant about coral reefs. Some 120 species are known, many reaching a very large size, and being also remarkable for their variegated coloration. The genera are mostly founded on the dentition, which shows much diversity; the following are the principal:—Myroconger, Enchelycore, Muraena, Thyrsoidea, Lycodontis, Pythonichthys, Echidna, Channomuraena. The Muraena of the ancient Romans, Muraena helena, of the Mediterranean, Eastern Atlantic, and neighbouring parts of the Indian Ocean, occurring exceptionally as far north as the English coast, grows to 4 feet, and its flesh was more esteemed than that of any other Fish, large numbers being reared in specially constructed reservoirs near the sea, and fed on the corpses of slaves. Channomuraena vittata, from the coast of Cuba, is known to attain a length of 8 feet, and Thyrsoidea macrura, from the Indian Ocean and the Malay Archipelago, to upwards of 10 feet.
Sub-Order 5. Haplomi.
Air-bladder, if present, communicating with the digestive tract by a duct. Opercle well developed. Pectoral arch suspended from the skull; no mesocoracoid arch. Fins usually without, rarely with a few spines; ventrals abdominal, if present. Anterior vertebrae distinct, without Weberian ossicles.
The absence of the mesocoracoid arch distinguishes the Haplomi from the Malacopterygii, with which they are united by various authors. They lead to the Percesoces through the Cyprinodontids, and to the Lower Acanthopterygians, such as the Berycidae, through the Scopelids, Stephanoberycids, and Percopsids, as is evidenced by the structure of the mouth and the forward position, in some of the genera, of the ventral fins, which, however, are never attached to the pectoral girdle. Most of the forms which are here included inhabit either fresh water or the deep sea.
Synopsis of the Families.
I. Parietals separating the frontals from the supraoccipital; post-temporal simple; praecaudal vertebrae with autogenous parapophyses.
Margin of the upper jaw formed by the praemaxillaries and the maxillaries; basis cranii simple; no adipose dorsal fin .......... 1. Galaxiidae.
Margin of the upper jaw formed by the praemaxillaries only; basis cranii double; adipose dorsal fin present .......... 2. Haplochitonidae.
II. Frontals in contact with the supraoccipital.