OSTEOLOGY OF BIRDS 



57 



" accessory pieces " as in some other falconine forms ; moreover, 

 these bones are very loosely articulated with the frontals on either 

 side, and they are sure to come away in the course of ordinary 

 maceration. From above we can also see the aliethmoids and the 

 anterior margins of the quadrates with the zygomatic bars leading 

 from them. The maxillaries show also upon this view, just beyond 

 the lacrymals. 



One of the most striking features upon basal view of the skull 

 of Circus is, how all the bones lie nearly in the same horizontal 

 plane, this plane extending from the posterior margin of the 

 foramen magnum to the descending hooklike process of the beak 

 formed by the premaxillary. This feature is quite characteristic of 

 some of the other genera, but not to the extent as seen in this 

 harrier. 



Just within the point of the beak are four small foramina, and 

 these openings are seen in other falconine species. Immediately 

 behind them we see in Circus the space where the palatines and 

 maxillopalatines merge into the premaxillary. On either side, and 

 external to this, is a foramen formed by the bones surrounding it 

 — the maxillary, the palatine and the dentary process of the pre- 

 maxillary. 



The major part of the palatines lie in the horizontal plane ; they 

 are broad behind, where they are marked on their inferior surfaces 

 with shallow depressions, to run out into narrow bars anteriorly. 

 The interpalatal space is broad, being fully three millimeters across 

 its narrowest part. In this space we see the vomer and the maxillo- 

 palatines. A small part of the palatines posteriorly curve upward, 

 affording by their firmly united superior surface a concave groove 

 to ride upon the rounded surface offered by the anterior half of 

 the rostrum, while beyond this they anchylose in the median line 

 with the vomer [fig. 23]. The articular heads of the palatines also 

 rest upon the rostrum, side by side, with their facets looking almost 

 directly backward to articulate with the pterygoids. 



The vomer [fig. 23] can best be studied in a longitudinal and 

 vertical section of the skull, passing very slightly to one side of the 

 median line. This I have been enabled to perform on one skull by 

 means of an exceedingly fine jeweler's saw. The appearance upon 

 the cut side of such a section is well seen in the figure referred to, 

 where the position of the vomer, there marked v, can be easily 

 observed. It is seen to be a thin lamina of bone, flattened from side 

 to side, and shaped much like a long S. Its anchylosis with the 



