Osteology of Circus hudsontus. 3 
its margin is produced backwards, forming the border of the den- 
tary process of the premaxillary, it again becomes convex from 
above downwards. ‘This latter convexity forms quite a percepti- 
ble 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 middie 
of the nasals, and merging into the above mentioned longitudinal 
one, which latter is then produced backwards nearly to meet the 
ethmoid, while anteriorly it gradually slopes downwards and for- 
wards by a gentle convexity to merge into the margin of the 
anterior third of the osseous nostril. 
As is the case in nearly all birds, the posterior boundary of this 
nostril is formed by the zasa/, which bone in the present subject, 
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 premaxil- 
biry . (Big. 2), We are likewise enabled to see upon lateral 
view the extensive maxzllo-palatines of this Hawk. ‘These very 
delicate bones are of a highly spongy texture here, and rise up 
nearly as high as theethmoid. Anteriorly they attach themselves 
both to the nasals and the inter-nasal septum. As they are pro- 
duced backwards they lie nearly parallel to each other, an inter- 
space existing of about two millimetres into which the vomer 
extends in the median plane. Below, their tissue is a little denser, 
their borders are rounded, while they merge into each other ante- 
riorly on this aspect with the palatines and premaxillary (Fig. 3). 
Their union with each maxillary is through a horizontal plate, 
which is not perforated by any foramina. The /acrymal of Circus 
is quite a large bone, as it is in most Hawks. It articulates with 
the frontal alone,;on an extensive facet situated on the extreme 
anterior and outer margin of that bone, just where it is overlapped 
by the nasal. From this point the lacrymal throws out, horizon- 
tally, being at the same time directed somewhat backwards, a 
broad ‘‘superciliary process'’ (Fig. 2), while it sends down- 
wards a flattened and much smaller process, concave in front, 
convex posteriorly, which touches by its apex the maxillary bar 
(Pig... 1), 
At the postero-external margin of either lacrymal there is 
