L UNO-FISHES. 463 



The genus Ceratodus was originally named by Agassiz, 

 from teeth found in Jurassic and Triassic strata in Europe. 

 Living specimens were found by Mr. Krefft in Queensland, 

 Australia, and called Ceratodus Foster i Krefft (Fig. 420). 

 This fish is rather more elementary in form than Lepidosiren, 

 the body being stouter, and the large scales of the body, 

 witli the fin-like paddles and distinctly rayed vertical fins, 

 cause it to resemble more closely ordinary bony fishes than 

 Lepidosiren (Giinther). Moreover, the lung is single, and 



Fig. 420. Ceratodus, or Australian Lung-fish. (The tail in nature ends in a 

 point.) After Gtinther; from Nicholson. 



not used so much as the two perfect lungs of Lepidosiren. 

 It attains a length of six feet. It can breathe by either gills 

 or lungs alone. When, Guuther thinks, the fish is com- 

 pelled to live during droughts in thick muddy water charged 

 with gases which are the product of decomposing organic 



Fig 4?l.Protopterus annectena, a lung-fish of Africa. (One-third natural size.) 



matter, it is obliged to use its lungs. The gills are more 

 like those of ordinary bony fishes than those of Lepidosiren. 

 It lives on the dead leaves of aquatic grasses, etc. The 

 local English name is " flat-head," the native name being 

 "barramundi." Little is known of its breeding habits or 

 mode of development. The eggs when ready to be laid arc 

 2.5 millimetres in diameter. The lower part of the oviduct 

 is much as in Menopoma. Fossil teeth of Ceratodus occur 



