LUNG-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 Fosteri Kreftt (Fig. 420). 
This fish is rather more elementary in form than Lepidosiren, 
the body being stouter, and the large scales of the body, 
with 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 Gunther; 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, Giinther 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. 421.—Protopterus annectens, 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 Leptdosiren. 
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 are 
2.5 millimetres in diameter. The lower part of the oviduct 
is much asin Menopoma. Fossil teeth of Ceratodus occur 
