The last six or seven caudal vertebrae coalesce into the pygostyle, an upright blade which carries the rectrices.
Caudal vertebrae more than thirteen, without a pygostyle, but with about twelve pairs of rectrices.
Ten remiges and ten rectrices.
The tail, in most species very short, has in others the middle feathers much elongated, and in one of the outer rectrices are attenuated and produced into threads.
2 Unless it be Oreopsittacus arfaki, of New Guinea, remarkable as the only parrot known as yet to have fourteen instead of twelve rectrices.