Fishes . HE Lung-fishes. — The group of Dipneusti, or Iving-fishes, is characterized by the presence of paired finsconsisting of a jointed axis with or without skull is autostylic, the upper jaw being made as in theChimasra of palatal elements joined to the quadrate and fusedwith the cranium, without premaxillary or maxillary. Thedentary bones are little developed. The air-bladder is cellular,used as a lung in all the living species, its duct attached to the. Fig. 170 —Shoulder-girdle of Neoceratodus foraUri Giinther. (After Zittel.) ventral side of the oesophagus. The heart has many
Fishes . HE Lung-fishes. — The group of Dipneusti, or Iving-fishes, is characterized by the presence of paired finsconsisting of a jointed axis with or without skull is autostylic, the upper jaw being made as in theChimasra of palatal elements joined to the quadrate and fusedwith the cranium, without premaxillary or maxillary. Thedentary bones are little developed. The air-bladder is cellular,used as a lung in all the living species, its duct attached to the. Fig. 170 —Shoulder-girdle of Neoceratodus foraUri Giinther. (After Zittel.) ventral side of the oesophagus. The heart has many valves inthe muscular arterial bulb. The intestine has a spiral teeth are usually of large plates of dentine covered withenamel, and are present on the pterygo-palatine and splenialbones. The nostrils are concealed, when the mouth is closed,under a fold of the upper lip. The scales are cycloid, mostlynot enameled. The lung-fishes, or Dipneusti (Sis, two; nvelv, to breathe),arise, with the Crossopterygians, from the vast darkness of * This group has been usually known as Dipnoi, a name chosen by JohannesMiiller in 1845. But the latter term was first taken by Leuckart in 1821 asa name for Amphibians before any of the living Dipneusti were known. Wetherefore follow Boulenger in the use of the name Dipneusti, suggested byHseckel in 1866. The name Dipnoan may, however, be retained as a ver-nacular equivalent of Dipneusti. 235 236 Subclass Dipneusti, or
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