6390 GEOLOGICAL SURVEY OF THE TERRITORIES. 
the superior mandible, both above and below, are mutually contluent at 
all their usual points of contact and articulations, with complete oblit- 
eration of their original borders. The nearly perpendicular nasals on 
either side form the anterior boundary of a triangular opening, of which 
the lacrymals and maxillaries form, respectively, the posterior boundary 
and base. These triangles are not complete, insomuch as the lacrymals 
do not meet the infraorbital bars at the inferior and inner angles. They 
lead into the rhinal vacuity on either side. It must be borne well in 
mind by the reader that in describing the upper mandible in the skulls 
of all birds, it invariably presupposes the removal of its horny integu- 
mental sheath that it wears during life, and gives to this portion of the 
cranium a vastly different shape. Hither tomial edge is curved and 
quite sharp; their anterior mergence, or point of the beak, is decidedly 
rounded, and fully a millimetre in width. 
The superior mandible is rather broad at its base; the culmen, origi- 
nating in a flattened space just anterior to the fronto-mandibular artic- 
ulation, is rounded throughout its extent and gently curved downwards, 
while below, the line joining the middle points of the bases of the triangles 
above mentioned, averages 7 millimetres in length. The sides of the in- 
ter-maxillary are smooth, presenting only occasionally a row of very mi- 
nute foramina for examination; sometimes a faint suture shows itself on 
either side, extending almost down to the nostril, between this bone and 
each nasal. Beneath, the palatine fissure is broad and rounded ante- 
riorly, the roof of the mouth beyond being gently concave and grooved 
mesially for its entire length, and marked by a few foramina. The ex- 
ternal apertures of the nostrils are quite large, nearly elliptical in out- 
line, approaching each other within less than .5 of a millimetre above. 
Their borders, formed by the nasals behind, are sharp; anterior, more 
rounded. The major axes of these openings average 4 millimetres, 
the corresponding minor axes 3 millimetres. The planes passed through 
their peripheries look upward, outward, and forward. The nasals are 
fan-shaped, both above and below, the expansion being slightly twisted, 
in order to accommodate themselves to the form of the bill. The broad 
lacrymals, assisted by the prefrontal, effectually separate the orbital 
vacuities from the rhinal chambers. The latter are more than usually 
open, owing to the size in the skull of the various apertures leading into 
them from without, already described, and devoid of all septa or bony 
offshoots, although the prefrontal, intermaxillary, and palatines to- 
gether occasionally develop irregularly formed ethmo-turbinals, that 
extend into this space from behind and afford the necessary surface for 
the pituitary membrane. But there is nothing that has the slightest 
semblance to an osseous septum narium. The anterior olfactory fora- 
mina, narrow slits one millimetre long, are found between the lacrymals 
and prefrontal, close to the vertical septum of the latter; their outer ex- 
tremities being the superior, they are seen to look downward and for- 
ward as they open into the nasal cavities from the bases of the concavi- 
ties formed by the bones above mentioned. 
The orbital cavities are capacious, having rather a forward look; at 
the same time they look a little downward. Their limiting borders are 
ovate in outline, with the greater end backward, being incomplete be- 
low. Anteriorily the septum that divides them is remarkably entire and 
of considerable thickness; posteriorly and above there exists quite a 
deficiency, of a shape shown in Pl. IV, Fig. 22; this is situated just in 
front of the large quadrilateral rhinencephalic foramen, and allows a good 
passage from either orbit into the brain-case. The same condition ob- 
tains below with the opening for the exit of the optic nerves, only the 
