“Tree-Ducks’ of the genus Dendrocygna. 53 
portions for the Ducks, Geese and Swans, some few differences might 
be met with; but in the present work I have not undertaken such 
comparisons.!) 
There seems to be considerable similiarity, with respect to the 
several bones of the manus throughout the Anseres, in so far 
as the morphology of them is concerned. Proportionately, they are 
found to differ in lengths, with respect to the bones of the arm and 
forearm in any particular species; but this has nothing to do with 
the characters they present. 
Dendrocygna autumnalis (454) has the carpo-metacarpus 
very long, in agreement with the other long bones of its wing. It 
measures 59 mm in length, and in its general facies and character 
it closely resembles the corresponding bone in Olor columbianus, 
which latter has a length of 120 mm. The shafts of second and 
third metacarpals are quite straight and nearly parallel to each 
other. Among the Anatinae the third metacarpal is almost always 
inclined to be more bowed, the concavity being toward the main 
shaft of the bone. This is decidedly the case in ducks with relatively 
short carpo-metacarpals, as C'henonetta jubata, Aix sponsa, and probably 
many others. The proximal head of the bone is always large, and 
the coossified first metacarpal prominent, especially in the Swans, 
where we find, too, that, at the distal end of the bone, the shaft 
of the third metacarpal is somewhat longer than the second, which 
is likewise the case in Dendrocygna, but not in Chen and most 
Anatinae. Pollex digit hasa length of about two centimeters 
in D. autumnalis, and is much compressed from side do side, though 
only its anterior border is at all sharp. Distally, it bears a small, 
free claw, as do both the ducks and the swans.’) 
There is also a free claw articulating with the extremity of 
the distal phalanx of the index digit, which latter is somewhat 
smaller, but has much the same form as the pollex digit. The small, 
free phalanx of third metacarpal has a length of some 12,5 mm, 
and has a low, rounded elevation upon the middle of its posterior 
border. This phalanx does not bear a claw in Dendrocygna. 
1) Most of the skeletons of the Anseres in the collection of the 
U. S. National Museum are ligamentous preparations; and in such, these 
two bones of the carpal joint are firmly encased in the surrounding liga- 
ments, making proper examinations or observations impossible. 
2) PARKER, W. K., On the morphology of the Duck and Auk 
tribes, tab. 2 figs. 4 and 7, tab. 3 fig. 7. 
