CHAPTER XXXV 



SUBCLASS DIPNEUSTI,* OR LUNG-FISHES 



HE Lung-fishes. — The group of Dipneusti, or lung- 

 fishes, is characterized by the presence of paired fins 

 consisting of a jointed axis with or without rays. 

 The skull is autostyhc, the upper jaw being made as in the 

 Chimaera of palatal elements joined to the quadrate and fused 

 with the cranium, without premaxillary or maxillary. The 

 dentary bones are little developed. The air-bladder is cellular, 

 used as a lung in all the living species, its duct attached to the 



Fig. 381. — Shoulder-girdle of Neoceratodus forsleri Giinther. (After Zittel.) 



ventral side of the oesophagus. The heart has many valves in 

 the muscular arterial bulb. The intestine has a spiral valve. 

 The teeth are usually of large plates of dentine covered with 

 enamel, and are present on the pterygo-palatine and splenial 

 bones. The nostrils are concealed, when the mouth is closed, 

 under a fold of the upper lip. The scales are cycloid, mostly 

 not enameled. 



The lung-fishes, or Dipneusti (Sis^ two; Ttveiv, to breathe), 

 arise, with the Crossopterygians, from the vast darkness of 



* This group has been usually known as Dipnoi, a name cho.scn by Johannes 

 Miiller in 1845. But the latter term was first taken by Leuckart in 1821 as 

 a name for Amphibians before any of the Uving Dipneusti were known. We 

 therefore follow Boulenger in the use of the name Dipneusti. suggested by 

 Hsckel in 1866. The name Dipnoan may, however, be retained as a ver- 

 nacular equivalent of Dipneusti. 



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