Osteology of Circus hudsontus. 23 
the base of the triangle below. I give a posterior view of this bone 
in my ‘‘Osteology of the Cathartide,’’ in ‘‘Hayden’s 12th Annual,”’ 
p- 761, where it is compared with the bone as it occurs in other 
Hawks and Falcons. Say nothing of a very few, not weighty 
points of difference existing between the pelvis of Czrcus and the 
same bone as we find it in many of the Owls, we may state that, 
in general resemblance, the pelvis of this Harrier is far more like 
that of an Owl than it is like the pelvis of any of the true 
Falcons. The pubic bones of an Owl, however, are nearly of 
uniform calibre throughout, from acetabulum to extremity. (pee 
my figure of Aszo wzlsontanus in Coues’ ‘‘ Key to N. A. Birds,”’’ 
ad €d., p. 136). 
In all of these birds the pelvis isa pneumatic bone, and in C7zvcus 
this condition is partially extended to the first two free coccygeal 
vertebree, but not beyond them. 
In the pectoral arch we find that a scapula is broad and truncate 
posteriorly, with its apex drawn out into a spicular-form point. 
Its neck is thick and broad, being sub-elliptical upon section (Figs. 
7 and g); while on the articular surface it extends to the glenoid 
cavity, and is about half or a little more than that presented by the 
coracoid. Upon its under surface, close to the line of articulation 
with this latter bone, we find a circular pneumatic foramen, which 
is constant. This line of articulation runs out to the end of the 
scapular process of the coracoid, but beyond this the scapula is 
extended as a clavicular process which meets the head of the 
furcula (Fig. 9), thus closing in the tendinal canal. In my draw- 
ing of these bones in the ‘‘ Osteology of the Cathariidz,’’ there is 
a slight separation at the point just referred to, which is correct. 
The proper relations of these bones in C77cus are shown in Fig. 9 
of the present memoir. In C7ycws all the thoracic pleurapophyses 
“are overlapped by the scapula, except the last two pair, so we may 
judge from this that this bone is below the average length for 
birds, not reaching the anterior border of the pelvis. 
One would hardly expect from an examination of the sternal 
bases of the coracoids that they decussated in their grooves, as 
these parts are apparently exactly alike ineither bone. ‘The inner 
angle is carried out as a sharp point while the outer is a stumpy 
process (Fig. 7). A strong muscular l:ne marks the shaft ante- 
riorily, especially at its lower part, the shaft itself being stout and 
subcylindrical at its middle third. Just below the inner end of the 
