672 GEOLOGICAL SURVEY OF THE TERRITORIES. 
hemal spine, here fulfilling most important functions as the superior 
mandible, as it does throughout the class at large. In the Tetraonide, as 
in the vast majority of birds, the intermaxillary or the ‘‘premaxillary ” 
of some authors is of much stouter material than most other bones of 
the head, its use being a very obvious reason for this. (Plate V, Fig. 
51, N. Pf. ML, 1. ML.) 
From the moderately free fronto-maxillary and pseudo hinge-jeint, 
between the out-turned frontals, the culmen of this bone slopes by a 
gently increasing arc to the tip of the beak. This surface is rounded 
and split in two from the enlarged inner extremity to a point over the 
distal border of the nostril; this division lasts during life. The exter- 
nal nasal orifices are unusually large and sub-elliptical in outline. The 
head of the ethmoid shows in very young chicks, but is eventually cov- 
ered by this bone, which also fills in snugly the internasal space (Plate 
-X, Fig. 75). 
WAS 
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The osseous maxillary tomia are even sharper than when they were 
capped with the horny integumental sheath that the entire bill wears 
during life; they are produced backwards on a triangular process of the 
bone below the shaft of the maxillaries, touching them in the Quails. 
Centrocercus urophasianus. 
