148 THE ANATOMY OF VERTEBRATED ANIMALS. 



artery seems originally to have been given off from an eighth 

 aortic arch. 



It is a remarkable circumstance that, while the Dipnoi pre- 

 sent, in so many respects, a transition between the piscine and 

 the amphibian types of structure, the spinal column and the 

 limbs should be not only piscine, but more nearly related to 

 those of the most ancient Crossopterygian Ganoids than to 

 those of any other fishes. 



