Air-bladder without open duct. Opercle well developed, hidden under the skin; supraoccipital in contact with the frontals, separating the parietals. Pectoral arch suspended from the vertebral column, far behind the skull; no mesocoracoid. Vertical fins with spines. Ventral fins absent.
This division stands in the same relation to the Acanthopterygii as do the Apodes to the Malacopterygii. The single family is possibly derived from the Blenniidae.
Fam. 1. Mastacembelidae.—Body more or less Eel-shaped; a series of short spines detached from the very elongate dorsal fin, which is more or less confluent with the likewise very elongate anal fin. A single nostril on each side. Mouth not protractile, bordered by the praemaxillaries, to the upper border of which the maxillaries are attached. Gill-cleft inferior; gills 4; branchiostegal rays 6; no pseudobranchiae. Vertebrae numerous (72-95), the praecaudals with transverse processes bearing the ribs. Scales very small.
Carnivorous fishes, from fresh and brackish waters of Southern Asia and Tropical Africa. 33 species are known, referable to two genera: Mastacembelus and Rhynchobdella. The largest species reach a length of three feet. Little is known of their habits. Of the Indian Rhynchobdella aculeata, Day says it conceals itself in the mud and becomes drowned in water if unable to reach the surface, as it apparently requires to respire air directly.
Fig. 433.—Mastacembelus maculatus. × ½.
Sub-Order 12. Pediculati.
Air-bladder without open duct. Opercle large, hidden under the skin; supraoccipital in contact with the frontals, separating the parietals. Pectoral arch suspended from the skull; no mesocoracoid. No ribs, no epipleurals. Ventral fins jugular. Gill-opening reduced to a foramen situated in or near the axil, more or less posterior to the base of the pectoral. Body naked or covered with spines or bony tubercles.
A small, natural group, connected with the Acanthopterygii Jugulares through the Batrachidae, in which the elongate pterygials of the pectoral fin foreshadow the kind of arm ("pseudobrachium") which is more or less characteristic of these highly aberrant Fishes. As in the Batrachidae, the post-temporal is flat and ankylosed to the cranium, and the suprascapula is much elongated. The pterygials, two or three in number, are separated from the small scapula and coracoid by a broad ligament, the arm-like pectorals being more or less distinctly geniculated and inserted far back behind the cranium. The head is large, the basis cranii simple. The gills are reduced to 2, 2½, or 3. The spinous dorsal, if present, consists of a few rays, which may be modified into tentacles inserted on the head. Vertebrae 17 to 31.
Five families:—