“Tree-Ducks” of the genus Dendrocygna. 37 
Anserinae or Öygninae. They come much nearer to those 
bones in such a species as Aix sponsa than that of any other 
skeleton I happen to have at this time, but this does not include 
Aix galericulata. 
The Pelvis and Cocceygeal Vertebrae (Fig.5l, Pl. 8; 
Fig. 55, Pl. 8; Fig. 68, Pl. 9; Fig. 69, Pl. 10; Figs. 79. and 80, Pl. 10; 
Hie784,Pl>Tl; Bir 111, PL:16 and: Fig. 112, Pl. 16). - Apart from 
the mere matter of size, the pelvis of Dendrocygna autumnalis and 
D. bicolor practically agree both in their general and special characters. 
The pelvis in bicolor is somewhat larger than it is in autumnalis. 
Anteriorly, in the former, the iliac bones are broader, and their 
antero-lateral angles are more widely rounded off; but I am inclined 
to think that this is an individual difference and not a specific one. 
When viewed upon its dorsal aspect, the pelvis in Dendrocygna 
is seen to be very distinctive, in that it differs from the pelvis of 
any other duck known to me, in its being so narrow for its length. 
This fact will be appreciated by examining and comparing the 
numerous figures of anatine pelves on the Plates cited above. 
Seen upon this view, the preacetabulum portion of the pelvis 
(454) is narrower in the middle than it is either anteriorly or at 
the transacetabular diameter. This surface is for the most part 
concave, the infero-external border being quite so for its entire length, 
while the supero-internal one is convex and fused for nearly its 
entire length with the superior border of the neural cerest of the 
anterior portion of the sacrum. 
The sides of the postacetabular portion face almost directly 
outwards, and but very slightly upwards. 
The internal iliac border is in close contact with the sacrum 
for its entire length, all to a short distance posteriorly. Here, too, 
it usually has the first caudal vertebra, between its mesial posterior 
angle and the same angle of the ilium of the opposite side. Anteri- 
orly, the ilia shut the sacrum out of sieht all to the “crista”, of 
which latter we can see the superior border. In the postaceta- 
bular area, the sacrum occupies almost the entire space, its 
surface being somewhat concave throughout, and the vertebrae 
forming it completely fused together, with foramina remaining here 
and there among the transverse processes (Fig. 55, Pl. 8). 
An ilio-ischiatic posterior border of the pelvis is entire; its first 
or mesial half is concave forwards, while the outer half is convex 
posteriorly. 
