“Tree-Ducks” of the genus Dendrocygna. 51 
processes, tubercles and other characters still more subordinated. 
However, the radial crest here is lofty and long, being much curved 
toward the palmar side. In Olor, this crest is much lower, and 
extends still further down the shaft. The elegant humerus in 
skeletons of any of this genus is highly pneumatic, and extremely 
light for its size. Olor columbianus has the bone measuring 
23,2 cms in length; while in Olor buccinator it averages 25,5 cms 
in length. 
Everything else being equal, apart from the matter of size, it 
differs from the humerus in Dendrocygna and the Anatinae 
generally in having the superior or radial crest so low, and extending 
down the shaft so much beyond the inferior or ulnar one, whereas 
in the latter, or the ducks, the radial and ulnar crests are of about 
equal length, the former being, as a rule, but very slightly longer, 
— that is, it extends down the shaft a trifle further. 
It would appear that, in a number of ducks, the humerus may 
be non-pneumatic, as it is in Chharitonetta albeola and Polysticta. *) 
The peeuliarity of the humerus in Dendrocygna is its unusual 
length for the relative size of the bird. In D. autumnalis it averages 
22 mm longer than the keel of its sternum. In Polysticta stelleri its 
humerus is several millimeters shorter than the keel of its sternum; 
while in A‘x sponsa its humerus is 17,5 mm shorter than the keel 
of the bone in that species. This is also the case in most all ducks; 
though in such a species as C'henonetta jubata, the humerus of its 
skeleton measures 14 mm longer than the keel of its sternum. 
However this may be, the bone in Swans and Geese is always very 
much longer than the keel of the sternum of the skeleton of the 
same individual wherein the measurement is made; while in the 
Anatinae, with perhaps a few exceptions, it is always more or 
less shorter. 
With respect to the bones of the antibrachium and manus, 
1) In my Osteology of Birds, published by the State Museum at 
Albany, N. Y., I have briefly described a few more humeri of the 
Anseres; and, in referring to the humerus of the goose figured in 
NEwTon’s Dictionary of Birds (pt. 2, p. 439), I remark that it must 
have been drawn from one furnished by the common domestic goose, as 
the characters are quite different from what we find among the wild 
species of that genus or genera generally. It illustrates the article 
„humerus“ by Dr. Hans GADow, and not by Mr. BEDDARD as there 
stated (p. 325). 
AF 
