“Tree-Ducks” of the genus Dendrocygna. 35 
(454). When present in the dorsals, it is generally present and 
much larger in the cervicals. Three or four of the dorsal vertebrae 
in Dendrocygna autumnalis possess haemal spines or processes. 
The first one on the first dorsal is small, with its inferior border 
dilated. On the next two following they are much longer and 
broader antero-posteriorly, their lower borders being produced for- 
wards and backwards. The last one, if present, is shorter, but is 
formed like the other two on the middle dorsals just described. 
That there may be very decided differences in the arrangement, 
or what really amounts to number of the ribs in Dendrocygna 
autumnalis, with variations in the ultimate cervical and the 
dorsal vertebrae, the material before me at this writing 
abundantly proves. 
In the skeleton of this species of the genus in the Collection 
of the U. S. National Museum (No. 1491), I find there are five 
dorsal vertebrae that support ribs connecting with the sternum 
by costal ribs. Either costal border of the sternum of this skeleton 
possesses seven facets for articulation with costal ribs; two of 
these are evidently intended for the costals of the pelvic ribs, and 
this I find to be the case. Posterior to these, in this skeleton, there 
is also another pair of extremely slender pelvic ribs, which probably 
possess equally slender “floating ribs” that do not reach the costal 
border of the sternum on either side. The first three dorsal vertebrae 
here possess haemal spines, — the first one being low and bifid; 
the next deep and broad and directed forwards; while the ultimate 
one is shorter, narrower and directed backward. This arrangement 
is shown in fig. 40 of my “Osteology of Birds” (in: N. Y. State 
Museum) on p. 312.%) 
One of the skeletons of Dendrocygna autumnalis (454), collected 
for me by Mr. F. B. Armstrong, has an arrangement altogether like 
this, with but one exception, namely: either costal border of the 
sternum- possesses but six facets for articulation with costal ribs 
(haemapophyses), and this is accounted for by the fact that the 
leading pair of pelviec ribs is the only pair articulating with the 
sacrum that connect with the sternum by means of costal ribs.. The 
pair next behind them have long, slender haemapophyses, which do 
1) In this specimen, the anterior portion of the pelvis and the last 
dorsal vertebra are twisted, — a condition which is probably pathological, 
though there is no evidence of disease. 
3*+ 
