STUDIES OE THE MACROCHIRES. 
323 
of the walls of this part of the cranium and how thin they are. 
Air seems to gain access to the major portion of the skull in both 
of these specimens, including the quadrates and perhaps the 
pterygoids. 
I am reminded in my examination of the 'mandible of Trogon 
of the form this bone assumes in some of the smaller American 
Owls, as Sjjeotgto for example. Its articular ends are rather 
large, being bluntly pointed behind, and having long, sharp, in- 
turned mesial tips. 
The borders of the rami are rounded off, while their height 
remains quite uniform for the entire length of the jaw. Upon 
their outer aspects, for the posterior moiety of each, an excavation 
occurs, at the middle of which, on either limb, is seen a small 
ramal vacuity. 
The symphysis is deeper by half again than either ramus, and 
the superior border above it is sharpened. In general outline the 
mandible of a Trogon is broadly V-shaped, and this bone is partially 
pneumatic. 
So far as these two specimens are concerned, I find that T. 
puella differs from T. mexicanus in its skull in having an entire 
osseous nasal septum, a rather wider frontal space on the superior 
aspect of the skull between the orbital margins, the parietal 
eminences are not so lofty, and a better developed osseous lip 
protects the entrance to the Eustachian tubes. Their mandibles 
are essentially similar. 
Of the Hyoid Arches . — As might be expected, these practically 
present little or no difference in the two species of Trogons 
before me. The hyoid arches in T. mexicanus are small as com- 
pared with the size of the skull of the bird, the thyrohyals barely 
curving up behind at all. The apparatus as a whole reminds me 
not a little of the hyoid arches in some of the smaller American 
Owls ( Glaucidium ). 
The glossohyal is formed entirely of cartilage, while the 
ceratohyals have ossified. In this adult bird the first and second 
basibranchials are joined in one piece by anchylosis, the cerato- 
branchial of the thyrohyals apparently articulating in the lateral 
sockets at their point of union. 
Cartilaginous tips finish off the hinder ends of the epibranchials, 
and these elements of the “ greater cornua ” are nearly straight 
longitudinally, nor are they notably curved in the direction of 
the median plane of the body. 
