Osteology of Circus hudsontus, 9 
while the formina for the internal carotids lay to their outer 
sides, posterior to them and just above the anterior tympanic 
recess. The foramina for the exit of the other cranial nerves 
that issue from the brain-case occupy their usual sites and offer 
nothing peculiar for description. They agree with Parker’s 
figure of the nestling Accipiter nisus. 
The condyle is hemispheroidal in form, and very small; it 
barely encroaches upon the periphery of the foramen magnum. 
This latter aperture is nearly round, and lies quite in the plane 
of the basi cranii. This condition seems to be characteristic of 
the Falconide. 
A posterior view of the skull of (zvcus presents a smooth, semi- 
globular surface. At its lower part, in the median line, we 
observe a _ well-developed supraoccipital prominence, with a 
decided concavity on either side of it. On this view we are 
just enabled to see the condyle, and only the outer projections 
of the quadrates. Laterally, the squamo-exoccipital wings hide 
other things from view beyond. Above these wings the sphenotic 
processes hang down. ‘The shallow median groove passes between 
the parietal. eminences. In the brain-case we observe (Fig. 5) 
that the carotid openings are separate, being some distance apart 
in the pituitary space. 
The wall covering the anterior semicircular canal is much 
raised, while beyond it the usual group of foramina for the exit 
of the seventh (the vagus) trifacial division of the fifth and other 
nerves are seen. 
The fossee for the lodgment of the several encephalic lobes are 
very deep, and this condition is heightened by an ossification of 
the tentorium, which divides them, for some little distance beyond 
the inner cranial wall along the site of the attachment ‘of that 
membrane. ‘The optic nerves make their exit at separate open- _ 
ings, already alluded to above. 
The greatest amount of diploic tissue is found between the 
inner and outer cranial tablets, at the vault of the cavity, or that 
portion covered by the frontal bones, as it is in these latter that it 
exists. In the superoccipital region it is quite scanty, and the 
cranial walls are here very thin (Fig. 3). 
Many of the bones in the skull of this Hawk are pneumatic, 
this part of the skeleton when dried weighing but thirty-eight 
grains (Troy), and this includes the lower jaw. 
