114 NE W YORK STATE MUSEUM 



sides being nearly parallel to each other and deep. The ischial 

 foramen is of great size, and the postpubic elements are entire. 

 This bone is very remarkable in other respects, and is a structure, 

 comparatively speaking, of great strength. The dorsal vertebrae 

 are not fused together, and the skeleton of the tail is somewhat 

 huge in its proportions, the ultimate vertebrae being massive. Tar- 

 so metatarsus is profoundly grooved down the anterior aspect of the 

 shaft; the longitudinal groove behind is likewise by no means shal- 

 low. The main, central, vertical plate of the hypo tarsus is long, but 

 not extended down the shaft as it is in Falco. A complete study of 

 the entire anatomy of this hawk should be made. M i c r a s t u r 

 ruficollis shows some few differences in its trunk skeleton ; I 

 have not seen the skull of this species. 



Ibycter a m erica n us offers a number of characters in its 

 skeleton that agrees closely with Polyborus, but there are also some 

 interesting departures. 



Milvago has many of the characters of Polyborus in its skull, 

 but in it the narial apertures are quite circular; the frontal region 

 on top is generally concaved longitudinally ; and the superior osseous 

 mandible is relatively not so deep in the vertical direction. The 

 skull is about one half the size of that of Polyborus. 



In the dorsal part of the spinal column in Milvago but three of 

 the vertebrae fuse together into one bone. In the skeleton of its 

 limbs it possesses all the essential characters in common with the 

 caracaras. 



We now finally have to examine the osteology of Pandion, the 

 Osprey, an accipitrine form .which possesses a skeleton exhibiting 

 characters entirely different from any representative of the group 

 thus far studied. In its general shape the skull of Pandion is more 

 elongated than it is in the true falcons, at the same time being rela- 

 tively narrower and of greater vertical depth. The contour of the 

 superior osseous mandible is far more like what we see in B u t e o 

 lineatus, than it is in Falco mexicanus; it has a 

 long, pointed hook at its apical extremity; the narial apertures are 

 large and subcircular, while the septum narium is always more or 

 less imperfectly ossified. Each nasal bone can be easily defined, and 

 the sutural lines between the nasal processes of the premaxillary are 

 open and distinct. This mandible is not toothed upon either tomial 

 edge, posterior to the apex — nor is the mediolongitudinal ridge upon 

 its buccal aspect, anteriorly, at all well developed. Superiorly, the 

 cranium is smooth, moderately wide between the orbital borders 



