Osteology of Circus hudsontus. 21 
mentioned (Fig. 7). I made many careful examinations and dis- 
sections of this bone in Czvcus before I was satisfied of what I 
saw, and that the condition existed as I have described it. In 
Falco sparverius the connection between these two separate parts 
of the pubic bone is through the finest imaginable bony bridge, 
that passes close under the margin of the lower ischiadic border, 
and so far as I have examined the Falcons it is always present in 
them, though sometimes almost of hair-like dimensions. 
Professor Owen says: ‘‘’The shortest pubis is seen in certain 
Eagles, in which it terminates after forming the lower boundary 
of the obturator foramen, its extremities there projecting freely, 
as in Fig. 23 (d@. Side view of pelvis, Eagle), or being joined by 
ligament to the ischium, as in the Harpy Eagle, in which it is an 
inch in length, whilst the ilium is six inches long.’ (‘‘ Anat. of 
Verts,”’ p. 36; Vol. IT). I am sorry to say that at the present 
writing I have not the complete skeleton of an Eagle before me, 
and no pelvis of that bird. I would not be surprised to learn, 
however, that the skeleton that fell to the lot of this eminent 
anatomist to examine at the time he made the above statement 
was an imperfect one, and that the hinder three-fourths of the 
pubis on both sides was lost, a thing very likely to happen were 
they connected to the anterior portion by a delicate bridge of 
bone, or entirely disconnected as we find them in Cz7cus. It may 
be that specimens of Cz7cus will be taken where the fine bony, 
almost hair-like, connection will be seen to join these two parts of 
the pubis, but so far I have failed to find one, and I must believe 
that the condition as I have described it above is the normal and 
perhaps constant one. Taking into consideration the state of 
these things as they exist in /alco sparverius it 1s very easy to 
conceive how such a condition might come about as we see it in 
Circus—the fine ligamentous span simply no longer ossifies—as 
whatever the original necessity was for weakening the pubis at 
this point it has been eventually accomplished, and ossification is 
now no longer extended to that part of the pubic rod at all. The 
free hinder ends of these bones in C77cus are now completely 
movable, as anyone can satisfy himself about by examining these 
parts in a freshly killed specimen. ' 
1Since writing the above I have detected this condition of the post-pubis in other 
Falconidz, and the reader is referred to my remarks about itin 7he Auk, January, 1586, 
p. 133, where I give a figure showing how it also occurs in Buteo borealis calurus. Professor 
W.K Parker, F.R.S., tells me, too, in a valued letter I have from him, that this state of 
things also occurs in some of the Old World Falconidz, and that in them the post-pubis is 
occasionally aborted, ‘‘ which is a very interesting fact.” 
