OSTEOLOGY OF BIRDS 53 



another convexity as it passes over the nostril to gradually 

 terminate, where its nasal processes articulate with the frontals 

 in the median line. The opposite or posterior margin of 

 the hook ahove mentioned is likewise convex anteriorly, and its 

 margin is produced backward, forming the border of the dentary 

 process of the premaxillary ; it again becomes convex from above 

 downward. This latter convexity forms quite a perceptible swell 

 in the bone, just before it receives the insertion of the maxillary. 

 The osseous nostril is elliptical in outline, and these two opposite 

 apertures are separated from each other to the extent shown in the 

 figure, by an osseous nasal septum. This septum has a transverse 

 partition, joining, but not rising above the middle of the nasals, and 

 merging into the above mentioned longitudinal one, which latter is 

 then produced backward nearly to meet the ethmoid, while an- 

 teriorly it gradually slopes downward and forward by a gentle 

 convexity to merge into the margin of the anterior third of the 

 osseous nostril. 



As is the case iii nearly all birds, the posterior boundary of this 

 nostril is formed by the nasal, which bone in this species has become 

 thoroughly incorporated, so far as its sutural borders are concerned, 

 with the other elements with which it comes in contact, with the 

 exception of the nasal process of the premaxillary [fig. 19]. We 

 are likewise enabled to see upon lateral view the extensive iiia.vil- 

 lof^alafiiics of this harrier. These very delicate bones are of a 

 highly spongy texture here, and rise up nearly as high as the 

 ethmoid. Anteriorly they attach themselves both to the nasals and 

 the internasal septum. As they are produced backward they lie 

 nearly parallel to each other, an interspace existing of about two 

 millimeters into which the vomer^extends in the median plane. Be- 

 low, their tissue is a little denser, their borders are rounder, while 

 they merge into each other anteriorly on this aspect with the pala- 

 tines and premaxillary [fig. 21]. Their union with each maxillary 

 is through a horizontal plate, which is not perforated by any 

 foramina. The lacryiiial of Circus is quite a large bone, as it is in 

 many of the Falconidac. It articulates with the frontal alone, on 

 an extensive facet situated on the extreme anterior and outer mar- 

 gin of that bone, just where it is overlapped by the nasal. From 

 this point the lacrymal throws out, horizontally, being at the same 

 time directed somewhat backward, a broad " superciliary process " 

 [fig. 20], while it sends downward a flattened and much smaller 



