/O NEW YORK STATE MUSEUM 



these two separate parts of the pubic bone is through the finest 

 imaginable bony bridge, that passes close under the margin of the 

 lower ischiac border, and so far as I have examined the falcons it 

 is always present in them, though sometimes almost of hairlike di- 

 mensions. 



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 

 figure 23 \_d side view of pelvis, eagle], or being joined by liga- 

 ment to the ischium, as in the Harpy eagle, in which it is an inch in 

 length, whilst the ilium is six inches long." [Anat. Vert., 2 136] I 

 am sorry to say that at 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 Circus. 

 It may be that specimens of Circus will be taken where the fine 

 bony, almost hairlike, connection will be seen to join these two parts 

 of the pubis, but so far I have failed to find one, and I must be- 

 lieve 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 F a 1 c o s p a r v e r i u s , it is 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 Circus are now completely mov- 

 able, as any one can satisfy himself by examining these parts 

 in a freshly killed specimen. 1 



The 20th and 21st vertebrae seen beneath the ilia have already 

 been sufficiently described. Posterior to them on the ventral aspect 

 of the pelvis a considerable swell takes place in the column to ac- 



1 Since writing the above I have detected this condition of the postpubis in other 

 Falconidae, and the reader is referred to my remarks abotit it in The Auk, January 

 1886, p. 133, where I give a figure showing how it also occurs inButeo borealis 

 c a 1 u r u s . This figure is herewith published in the present treatise as figure 47. 

 Prof. 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 Falconidae, and in them 

 the postpubis is occasionally aborted, " which is a very interesting fact." 



