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It is homologous with the distal ends of the ceratohyals or ventral elements of the hyoidean or second visceral arch.

These appendages are usually unilateral, and are derived from the second visceral arch.

From the hinder edge of the second visceral arch there develops, as Rathke had seen, a fold which is comparable with the operculum of fish.

The cartilaginous rod supporting the second visceral arch divides into three pieces on each side, of which the lower two form the hyoid, the uppermost the columella.

The first visceral arch, he found, gave in Amphibia practically the same structures as in the higher Vertebrates.