COLD-BLOODED VERTEBRATA 



383 



ward, but from side to side in a remarkable way. They lie 

 on one side, which is white and has lost its eye, this being 

 brought on to the upper, coloured side by a twist of the 

 skull in the region of the orbits. The body is very high — 

 that is, in its present position, broad. The young are 

 shaped like ordinary fishes. 



The Dipnoi are a small group of freshwater fishes of the 



iii. Dipnoi. tropics. They have bones, a gill cover, scales 



of the cycloid type, no spiracle, a conus 



arteriosus, thick-roofed cerebral hemispheres like those 



Fig. 276. 



-The Plaice (Pleuronectes platessa). 

 MacBride. 



-From Shipley and 



of a frog, internal nares, air-bladders which communicate 

 with the ventral side of the gullet and are used as lungs, 

 and a larva much like a tadpole. Thus in several features 

 they point the way to the Amphibia. 



The Amphibians differ from fishes and agree with higher 

 vertebrates in two important respects — their 



Amnhihin 



paired limbs are pentadactyle (p. 40), and if 

 they have unpaired fins these are without fin-rays. They 

 are also like the higher vertebrates in possessing lungs 



