The Dipnoi show a distinct transition between fishes and amphibia.
"Encyclopaedia Britannica, 11th Edition, Volume 2, Slice 8" by Various
In Protopterus among the Dipnoi it is enclosed within the walls of the stomach.
"Encyclopaedia Britannica, 11th Edition, Volume 8, Slice 8" by Various
This is especially the case with the Ganoids and the Dipnoi.
"The Chain of Life in Geological Time" by Sir J. William Dawson
There is again no indication of any close affinity between the Dipnoi and, at any rate, existing Ganoids.
"The Works of Francis Maitland Balfour, Volume 1" by Francis Maitland Balfour