“Tree-Ducks” of the genus Dendrocygna. 61 
in & conspicuous decurved nail; orbits of the eranium completely 
surrounded by bone, and having but seventeen cervical vertebrae. 
As thus constituted, this subfamily of ducks occupy, in any 
lineal scheme of classification, or in any sequential classificatory 
presentation — apart from a phylogenetic tree of birds — a place in 
the Anatidae, between theAnserinaeandtheChenonettinae, 
which is the position they hold in the system by virtue of the 
morphological characters they present in their structure. 
