FIFTEENTH STAGE: +Primaeval Amniota (Protamnia)+.
"The History of Creation, Vol. II (of 2)" by Ernst Haeckel
This is not the place to enter into the obscure question as to how far the ribs of the Amphibia and Amniota are homologous with those of Fishes.
"The Works of Francis Maitland Balfour, Volume 1" by Francis Maitland Balfour