26 Osteology of Circus hudsontus. 
The distal énd of the radius is somewhat expanded transversely, 
to allow room for the grooves for the passage of the tendons, and 
a small articulation for the base of the os prominens. Below occurs 
the usual facet for the vadzale. 
The olecranon of the z/7a is fairly well-marked as a rounded tuber- 
osity, extending some two or three millimetres beyond the circular 
and concave facet intended for the ulnar tubercle of the humerus. 
It also has the usual articular concavities for the oblique tubercle 
and the head of the radius. The shaft of the bone is nearly four 
times the bulk of the shaft of the radius in calibre ; it is cylindrical 
and but slightly curved, showing only very faintly the row of 
papillee for the quill-butts of the secondaries, adown its length. 
Nothing of marked importance presents itself for our examina- 
tion at the distal extremity of the ulna of C7zrcus. ‘The bone has 
here the usual articular surfaces and tuberosities for radiale and 
ulnare. Several years ago I described the ossicle of the anti- 
brachium, in the Wztlall Ornithological Bulletin, as it was found 
in Cz7vcus, and named it the os prominens referred to above. In 
that article I present a cut showing its relations to the neigh- 
boring bones and the insertion of the extensor patagu longus. 
(Oct. 1881). This ossicle had previously been noticed by Prof. 
A. Milne Edwards, in a Kestrilin his ‘‘ Essai sur Appareil Loco- 
moteur des Oisseaux.’’ Mivartin his ‘‘ Lessons in Elemantary 
Anatomy ’’ (p. 320) also gives a cut, (after A. Milne Edwards), 
showing its position in the wing of an Eagle (4guila fucosa). 
Later, (April, 1882), in the Nzttall Ornithological Bulletin, Mr. 
Frederic A. Lucas in his ‘‘ Notes on the Os prominens,’’ made some 
valuable additions to our knowledge of the subject, presenting a list 
of many Hawks and Owls in which it occurred, and gave excellent 
figures showing its position in Bubo virginicanus, Otogyps Calvus, 
and others. In the chapter on the Anatomy of Birds in the second 
edition of his ‘‘ Key,’’ Inote that Professor Coues adopts the name 
I originally bestowed upon this sesamoid. It seems that a bone 
which attains the size it sometimes does in certain birds, ought to 
be entitled to a distinctive appellation. 
The mefacarpus of this Harrier is a little over six centimeters 
long. Its articular surface for the carpal segments is quite oblique, 
and the part which originally was the first metacarpal, now forms 
an unusually prominent and projecting process, slightly bent to 
the anconal side. Wedged in between the proximal end of the 
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