The bones which bear the two occipital condyles have given rise to much discussion, and the definition given by Huxley in the previous edition - "two occipital condyles, the basi-occipital region of the skull either very incompletely or not at all ossified" - requires revision.
Some authors have held that the bone on which the occipital condyles have been found most developed in some labyrinthodonts (2) represents a large basi-occipital bearing two knobs for the articulation with the first vertebra, whilst the skull of the batrachians of the present day has lost the basi-occipital, and the condyles are furnished by the exoccipitals.
On the other hand, some reptiles have the occipital condyle divided into two and produced either by the basi-occipital or by the exoccipitals.
Woodward (3) to show that, in that form at any rate, the condyles are really exoccipital, although they are separated by a narrow basi-occipital.
The fact remains, however, that some if not all of the stegocephalous batrachians have an ossified basi-occipital.