Singularly shaped fishes, of rather small size, from the Mediterranean, the warmer parts of the Atlantic, and the Indian Ocean; of the ten species known one species only has been found in the Pacific, near the Sandwich Islands. The European species is P. cataphractum. They are not common, and probably inhabit greater depths than the Gurnards, with which they have much in common as regards their habits.
Fig. 216.—Dactylopterus volitans.
Dactylopterus.—Head parallelopiped, with the upper surface and the sides entirely bony; scapula and angle of the præoperculum produced into long spines. Body with strongly keeled scales of moderate size; lateral line none. Two dorsal fins, the second not much longer than the first; pectoral very long, an organ of flying, with the upper portion detached and shorter. Granular teeth in the jaws; none on the palate. Air-bladder divided into two lateral halves, each with a larger muscle.
Of “Flying Gurnards” three species only are known, which are very abundant in the Mediterranean, the tropical Atlantic, and Indo-Pacific. They, and the Flying Herrings (Exocoetus), are the only fishes which are enabled by their long pectoral fins to take flying leaps out of the water, and deserve the name of “Flying-Fishes.” They are much heavier, and attain to a larger size, than the Exocoeti, specimens of eighteen inches in length not being scarce. When young, their pectorals are much shorter, and, consequently, they are unable to raise themselves out of the water (Cephalacanthus).
The vertebral column shows a singular coalescence of the anterior vertebræ, which form a simple tube, as in Fistularia.
We insert here as an appendix to this division the small family of Pegasidæ, the natural affinities of which are not yet clearly understood, but which resembles in some of its characters the Cataphracti.
Fifteenth Family—Pegasidæ.
Body entirely covered with bony plates, anchylosed on the trunk and movable on the tail. Barbels none. The margin of the upper jaw is formed by the intermaxillaries and their cutaneous prolongation, which extends downwards to the extremity of the maxillaries. Gill-cover formed by a large plate, homologous to the operculum, præoperculum, and sub-operculum; interoperculum a long fine bone, hidden below the gill-plate. One rudimentary branchiostegal. The gill-plate is united with the isthmus by a narrow membrane; gill-openings narrow, in front of the base of the pectoral fin. Gills four, lamellated. Pseudobranchiæ and air-bladder absent. One short dorsal and anal fin, opposite to each other. Ventral fin present. Ovarian sacs closed.