32 Osteology of Circus hudsontus. 
hypotarsial process shrunk up to the merest apology for such a 
thing, while the inner one holds a mid-shaft position, becomes a 
very prominent crest, which is carried down the posterior aspect 
of the bone for fully two-thirds of its length, gradually disappear- 
ing in the middle of its lower third. Above, it is pierced on 
either side of the crest by a foramen, these being placed nearly 
side by side, with the wall of the crest, just described, between 
them. 
The proximal end of the first digit of Aa//wx is broad and sub- 
compressed ; the shaft of the bone is strong and stout—its upper 
aspect is rounded, while below it is flat and slightly grooved 
longitudinally. The trochlear surface is deeply scooped out in the 
median line, more especially underneath—an arrangement which 
allows the ungual phalanx to be thrown well towards the sole of 
the foot. Thus strongly flexed, this Harrier in common with 
other birds of prey can firmly hold the victims they seize, and 
even with ease drive their talons into their very flesh. The 
ungual phalanx of hallux is a powerful bone, curved throughout 
and sharp-pointed. When held in the position it has when the 
bird is standing, we observe the following points for examination 
at its proximal end, from above downwards. First, a single 
median process, the superior convex surface of which is contin- 
uous with the line of the upper border of the claw. This process 
has on its under side a raised median ridge for articulation with 
the superior groove of the trochlea of the first phalanx. It is pro- 
duced in the median line at an open angle over a circular projec- 
tlon below it. Here we find on either side of the ridge a con- 
cavity, the whole forming the articular surface for the inferior 
side of the trochlea of the first phalanx. Projecting in the 
median line downwards and backwards, from beneath the parts 
just described, another prominent process is seen, for tendinal 
insertion. First phalanx of hallux measures 1.8 centimetres in 
length ; the chord of the claw measuring two centimetres taken 
from apex to tip of that process which is the superior one when 
the foot is in the position of standing. 
The first phalanx of the inside toe is a chunky, and at first sight 
a very irregular shaped bone. 
Above, it is convex from side to side and presents a small 
tubercle on its inner aspect. Longitudinally the superior surface 
is limited, the two articular facets nearly meeting. Its lower sur- 
