As in the Haplochitonidae, the neural and haemal arches are bones distinct from the centra, and although parapophyses are not developed, the ribs are not inserted on the centra, but on distinct bases wedged into the latter.[[691]] Teeth are present on the vomer, palatine, and pharyngeal bones.
Fig. 368.—Skeleton of Esox lucius. (After Jordan and Evermann.)
A small family of carnivorous freshwater Fishes, including the Pike (Esox), of predaceous habits, unsurpassed in greediness and voracity, and the small and insignificant-looking Umbra, distinguished by the more anterior position of the dorsal fin, the larger scales, and the moderately large gape, with feeble villiform teeth. The range of the Esocidae is restricted to the cold and temperate parts of the northern hemisphere. Besides the well-known Esox lucius of Europe, Northern Asia, and the northern parts of North America, growing to a length of 4 feet, and the Maskinongy (E. nobilior) of north-eastern North America, reaching twice that length, the first genus comprises three smaller species from the Eastern United States. Remains of Esox have been found in various freshwater deposits in Europe as far back as the Oligocene. E. lepidotus, of which very perfect specimens have been found in the Upper Miocene beds of Oeningen in Baden, differs from the living species in its much larger scales and in the greater approximation of the ventral and anal fins, two characters in which it approaches Umbra. Only two species of the latter are known: U. crameri ("Hundsfisch"), from the stagnant waters of Austria-Hungary, and U. limi ("Mud-Fish"), living in swamps and ditches in Canada and the north-eastern United States, often remaining imbedded in the mud of prairie sloughs and bog-holes.
Fig. 369.—Distribution of the Esocidae.
Fam. 5. Dalliidae.—The genus Dallia, with a single species inhabiting the streams and ponds of Alaska and Siberia, is related to Umbra, but differs in the very thin and papery skeleton, with the post-temporal imperfectly ossified and the pectoral fin without pterygials or actinosts. The dorsal fin is far back and opposite to the anal, as in the Pike. The ventral fins are composed of three rays only, and the pectorals, which have a somewhat fleshy base, have as many as 36. The scales are extremely small, and partly imbedded in the skin. The Black-Fish, D. pectoralis, abounds in Sphagnum ponds, feeding on plants and worms, and forming the chief food of the natives of some parts of Northern Alaska, where, with the exception of the Salmonids, it is the only freshwater Fish. Turner, its discoverer, says its vitality is extraordinary: Black-Fishes will remain frozen in baskets for weeks, and when thawed are as lively as ever, one having been swallowed in a congealed condition by a dog, thawed out by the heat of the stomach, and vomited up alive.
Fig. 370.—Dallia pectoralis, ½ natural size. (After L. M. Turner.)
Fam. 6. Scopelidae.—Praemaxillaries much elongate, and completely excluding the maxillaries from the oral border. Supraoccipital in contact with the frontals, sometimes partly covered by the parietals; opercular bones all well developed. Basis cranii simple. Ribs sessile; no parapophyses on the praecaudal vertebrae; epipleurals and epineurals. Post-temporal forked, the upper branch in contact with the epiotic or the supraoccipital, the lower with the opisthotic; post-clavicle present. An adipose dorsal fin often occurs; luminous spots often present on head and body. Ventral fins with 7 to 10 rays. Air-bladder sometimes absent.