30 Osteology of Circus hudsonius. 
condyle a hemispherical tubercle forms a striking object. Czrcus 
has but a single patella. This bone is of a cordate form with the 
rounded apex below, and a transversely truncate surface above. 
Posteriorily it is more convex than it is anteriorily, and it has a 
transverse diameter of five millimetres at it greatest width. 
The jdula (Figs. 12 and 14) is laterally compressed above, the 
hinder part of its head extending backward over the shaft. It 
does not rise above the articular plane of the tibia, and only 
touches it above near its anterior and innerangle (Fig. 14). At 
1.3 centimetres down its shaft it comes in contact with the fibular 
ridge of the tibia, opposite which it develops on the outer side of 
its shaft the usual tuberosity for the insertion of the tendon of 
the biceps. Its contact with the fibular ridge extends for two 
centimetres along the tibial shaft. Be‘ow this the fibula does not 
again come in contact with the latter until it passes its middle 
point from whence its needle-like dimensions may be traced in 
close contact with the main bone of the leg to the juncture of its 
middle and lower thirds. 
The Marsh Harrier presents us with a very interesting form of 
a farso-metatarsus, (Figs. 13, 15 and 16). Viewing its proximal 
extremity directly from above, (Fig. 15) we note that there are two 
distinc: processes representing the ‘‘hypotarsus.’’ ‘The inner of 
these is the longer, and both have slightly dilated extremities. 
They are at right angles to the shaft, and separated from each 
other by an interval of four millimetres, the base of the intervening 
valley being roundly concave from side to side. ‘The articular 
surface at the extremity of the tarso-metatarsus preseuts two well- 
marked depressions for the condyles of the tibia. They are sep- 
. arated in the middle line by aslight convexity. Upon direct front 
view this bone appears to be straight, but seeing it laterally shows 
it to be greatly curved from one end to the other, the concavity 
being along the front of the shaft. It is much scooped out ante- 
riorly, just below the articular end (Fig. 13). ‘This is continued 
a short distance down the shaft, trending towards the inner side. 
At its deepest part, above, the bone is pierced from before, back- 
wards, by a single foramen. Below this, and rather to the outer 
side there is a small, elongated, though prominent tubercle. Run- 
ning down the front of the shaft from a point on the periphery of 
the proximal end, opposite the middle of the external articular 
depression for the condyie of the tibia, to the middle of the outer 
—————— Em 
