38 R. W. Skureuor, 
On a lateral view, we are to note the large, circular aceta- 
bulum, with its mesial periphery but slightly smaller than its 
outer, with a conspieuous antitrochanter occupying its usual 
site in the postero-superior arc of the latter. 
As in all Anatidae, a well-marked prepubic spine is 
present, while the pubic element itself is long and very slender. 
It assists in elosing a small, elliptical obturator foramen, and 
a long, rather narrow obturator space. Its free end, posteriorly, 
is not in any way dilated, as in the Geese and Swans, but of the 
same uniform width as in the true ducks. For about the distance 
of a centimeter, more or less, it is in contact with the free margin 
of the infero-posterior border of the ischium (Fig. 112, Pl. 16). 
Agreeing with most Anseres, a spacious ovo-elongate ischiac 
foramen monopolizes a large part of the post acetabular space 
on the lateral aspect of this pelvis. Its broad end is immediately 
behind the antitrochanter. 
Ventrally, the pelvis of Dendrocygna has a distinct anterior 
portion Ilying beyond the prepubic spines.. This is narrow, and 
almost entirely filled in with the coössified anterior sacral vertebrae, 
the six or seven pairs of transverse processes of which extend out- 
wards to almost reach the free margin of the ilium on either side. 
Posteriorly, the pelvic basin is deep and narrow, its mesial 
portion being occupied by the remainder of the sacrum, the trans- 
verse processes of the vertebrae of which stand out with marked 
prominence, they being directed backwards and outwards. 
The caudal vertebrae are small, and their usual spines and 
processes very indifferently developed. They terminate as a very 
much elongated and by no means insignificant pygostyle. 
This pelvis of Dendrocygna I have compared, character for 
character, with the pelves of many species of ducks, mergansers, 
geese and swans, and it seems to have in its composition a curious 
and interesting mixture of them all. It has the elongate general 
form of the pelvis of the swan (Olor); but the latter has the immensely 
dilated distal ends to its pubice bones, and there is a deep ilio- 
ischiae notch on the posterior pelvie border, which, in Drant« 
canadensis, is converted into a foramen by the ilium and ischium 
again closing in behind it. Olor may have as many as five pairs 
of pelvie ribs; Dranta four, and Dendrocygna never more than 
three as in Mergus serrator, Harelda and other ducks. 
But the pelves of most Anatinae are narrow for their 
