736 GEOLOGICAL SURVEY OF THE TERRITORIES. 
such as we offer in Plate XV, fig. 105, G. papa, we are struck with the vul- 
turine appearance of the skull, with its more or less open, capacious ex- 
ternal nasal orifices, its hooked beak, its rather large orbital cavities 
and the good size of the bones at the bases of these orbits. The seg- 
ments of the vertebral column, or the vertebre, are all free, from oc- 
ciput to sacrum, with their processes and arches well developed. We 
observe, too, the great length and size of the bones of the extremities ; 
particularly those of the brachium and anti-brachium of the upper, and 
the robust femora of the latter. To support these great limbs, we find 
these birds possess correspondingly well developed arches of the axial 
skeleton. Nor are the bones of the feet backward. in indicating to us 
the avocation of their owners, attached as they are, too, to powerful 
leg bones. In short, the Cathartide must be regarded as possessing 
skeletons composed of bones above the average, for the size of the 
bird, in point of volume and length. These characteristics, however, 
do not bring with them a correspondingly heavy skeleton, but quite 
the contrary, for if we pick up the bony framework of any of our Vul- 
tures we cannot help but being struck by its unusual lightness; this is 
due to almost a universal pneumaticity of the bones composing it, and 
so marked a feature is this of the birds we are describing that it will 
not be considered out of place to give a general description of this 
condition here, so as to avoid, as much as possible, what would have 
to be a constant reference to the many pneumatic foramina that occur 
in nearly all of the bones that we shall come to describe further on. 
Let us choose a specimen of Catharista atrata that we have before us 
for this purpose, simply reminding the reader that at least some of 
these openings will necessarily have to be referred to again, while with 
others their description will cease here. In the skull of this Vulture, 
as in all others of the family, the only elements that seem to possess 
this property are the quadrate bones (the tympanics of my former 
papers), the posterior thirds of the limbs of the lower mandible, and 
the lacrymals. In the quadrate bones we usually find a single, rather 
large, sub-elliptical opening at the bases of the mastoid ends or pro- 
cesses with a large one at their summit in Pseudogryphus—while several 
such foramina occur on the superior aspects of the articular extremities 
of the lower jaw; two of these latter seem to be constant and are found 
towards the points of their in-pointing prolongations. On the inner 
aspect of the lacrymals we find either one such pneumatic orifice or a 
group of several of them, and the air seems to attain complete access 
to these bones, and perhaps enters to a limited extent the wings of the 
ethmoid that they anchylose with on either side. It is very apparent 
that the walls of the brain-case or the bones that go to form the beak 
could not afford to make any such sacrifice of stability for the little 
additional lightness that would be gained thereby—the functions of 
these parts would evidently be weakened by it, affording as it would 
insufficient protection for the brain, and rendering the beak constantly 
liable to fracture. 
The author is free to confess that at the present writing he knows 
not of a single instance among the class where to look for a bird pos- 
sessing an atlas endowed with this property, and we find here in the 
Cathartide again, this bone apparently solid, or at least absolutely non- 
pneumatic, while the following vertebra, the axis, is quite so. Consti- 
tuting, as its occurrence does in this bone, rather an uncommon condition 
for it, knowing as we do that in many birds where every vertebra will 
be cued to be pneumatic, the atlantal and axial segments remain ex- 
empt. 
