748 GEOLOGICAL SURVEY OF THE TERRITORIES. 
standpoint (see plates of skulls), it presents for our examination, in addi- 
tion to other points that we have already considered, 1. The entrance to 
the organ of hearing; 2. Two prominent processes; 3. The general sur- 
face. : 
The posterior boundary to the aural aperture is formed by a strong, 
raised, semi-elliptical rim, the upper border of which is produced for- 
wards in all of the Cathartide to terminate in a horizontal and conical 
apophysis, one of thetwo mentioned above. (Fig.113,Plate XX.) This 
flaring entrance to the ear gives us a very good opportunity to examine 
into some of the osteological features of this organ as seen in the vultu- 
rine head. We observe the funnel-shaped opening of the Eustachian 
tube; the foramen leading to the inner ear, as well as several vascular 
foramina. 
In fact, in our California Condor, so shallow is this outlet that by the 
inexperienced it might be easily overlooked as not forming any part of 
the aural apparatus. 
The remaining process found on the lateral aspect of these skulls is 
above the one we have just described, and is directed almost directly 
‘Jownwards. having only a slight inclination outwards and forwards. 
We are of the opinion, and believe our reader will agree with us after 
an exanvpation of the segmented cranium that we presented in the 
Tetraonide, that this process was no doubt developed by the alisphe- 
noid. 414 becomes compressed from side to side in Neophron, still more so 
in the Secretary Vulture, while it is positively wing-like in Aquila cana- 
densis and in the majority of the Hawks and Owls. The intervening 
valley between these two processes is roundly concave, as the squamosal 
surface of this lateral aspect is generally convex outwards above and 
slightlv concave below, forming, as it does, the temporal fossa on either 
side, and showing a limital muscular line above. The uppermost of these 
two processes is called the sphenotic. 
The posterior wall of the orbital cavity is quite smooth and concave 
from above downwards in C. aura and C. atrata, less so in G. papa, while 
in Pseudogryphus and the South American Condor it is nearly flat and 
slopes away rapidly towards the sphenoidal suture, being marked by 
several transverse lines or ridges. The “foramen ovale” is unusually 
large in these birds, and is to be found rather low down in the orbit, 
almost hidden in the shadow of the great quadrate bone on either side. 
Passing to the basi-cranii we find in Cathartes and Catharista the fora- 
men magnum to be nearly circular in outline, while in Pseudogryphus and 
Sarcorhamphus its vertical diameter is the longer. The bony walls of the 
back of the brain-ease project beyond this important aperture in the 
median line and with a gradually lessening amount on either side, due 
to the fact that these birds all have long and markedly prominent “ cere- 
bellar prominences,” which rise, dome-like, above the foramen of the oc- 
ciput. This is strikingly the case in Pseudogryphus, in which, as among 
others of the Cathartida, the inferior border ofthe cerebellar prominence 
and the superior arc of the foramen magnum lie in the same line, which 
line slopes away_on either side to terminate in the paroccipitals or lower 
angles of the raised ridges that bound theears. This line or ridge forms 
a striking feature in rear views of the skulls of the Cathartide, and is 
present to a greater or less degree in many of the diurnal and nocturnal 
Raptores. Thecondyle, situated at its usual site inthe median line, fairly 
on the lower border of the foramen magnum, is broadly and transversely 
elliptical; in fact, it may be said to be semi-ellipsoidal in form and non- 
pedunculated, though prominent. It has a faint median notch above in 
all except Pseudogryphus, where it is very feebly marked, if it occurs at 
all. We have specimens of C. atrata before us in which the occipital 
