612 SHUFELDT—OSTEOLOGY OF THE WOODPECKERS. [Oct. 5, 
The calibre of the neural canal is subcircular and not large, and 
swells but little for the enlargement of the myelon where the sacral 
plexus is given off. One thing strikes us as peculiar in this pelvis, 
and that is upon its ventral aspect there is no lengthening nor any 
other change in the transverse processes of the vertebrz opposite 
the acetabule. It is well known that in a great many birds these 
are increased in size and strength and thrown out as_ buttresses 
against the ilia as a means of support for these points, they being 
opposite the articulation of either femur. Anteriorly there are 
three vertebre that throw out their diapophyses against the ilium 
on either hand. 
In Dryobates the general character of the pelvis is the same, 
presenting but few specific differences. Viewed from above thiere 
is seen to be a flush, smooth and level area mesially situated be- 
tween the points where the ‘ ilio-sacral canals’’ terminate behind 
and a pair of triangular depressions over the sacrum posteriorly .for 
the lodgment of caudal muscles. This is also fairly well marked in 
Colaptes. In Xenopicus the pelvis is very much like that bone in 
Dryobates, while in Picoides arcticus it has a pattern peculiarly its 
own. Here the pelvis is short antero-posteriorly, with very deep 
sides, and post-pubic elements scarcely produced at all behind. 
Moreover, in Picotdes the obturator space is shut off by bone from 
the large subcircular obturator foramen, and the downward project- 
ing process of either ischium behind is exceedingly small. 
The pelvis of Melanerpes torquatus reminds me very much of 
the pelvis in Colapfes, it having the same general character and 
form. The same remark applies, though not so strictly, to the 
bone as we find it in JZ. carolinus. 
In the Ivory-billed and Pileated Woodpeckers the pelves much 
resemble each other, but in the first-mentioned species the side of 
the bone posterior to the acetabulum is comparatively much deeper, 
while in the Pileated Woodpecker the descending foot of the 
ischium is relatively much broader and always fuses with the supe- 
rior edge of the post-pubis where it meets it. In both these species : 
the pelvis is largely pneumatic, a condition that obtains to a greater 
or less degree for this bone in all of our Prez ; least so, perhaps, in 
such a type as Sphyrapicus. Sphyrapicus v. nuchalis has a pelvis 
quite picine in all its characters. Some good distinctive features 
present themselves when we come to compare such a pelvis with 
the pelvis of Zyrannus tyrannus. 
