320 DR, R. w. siiueeldt’s morphological 
is this true of the superior vacuity. In both of these Trogons, 
however, although these foramina are very large, they still retain 
their individuality, and do not merge with each other. 
At the upper part of the interorbital septum we observe, 
plainly marked, the track for the first pair of nerves. It does 
not in either of these specimens communicate, through a thinning 
of the walls, with a similar track in the opposite orbital cavity, 
as we often see in other birds. 
Anteriorly the partition between the orbit and rhinal chamber 
is composed of an exceedingly small pars plana , and of a thin 
membrane which stretches from it to the already-described lacry- 
mal bone. In the dried skeleton, after the membrane has been 
removed, the communication between these two cavities is un- 
usually free, more so than in any other bird that I happen to 
recall at the moment. The periphery of the orbit is sharp for 
its anterior two thirds, but becomes rounded olf as it passes 
backwards over the anterior wall of the brain-case in line with 
the lateral processes of the skull. 
Sutural traces among the original elements composing the 
quadrato-jugal bar are hardly perceptible, and this osseous rod is 
quite straight from one end to the other, its tip only being bent 
up as it articulates with the quadrate. 
Each nasal bone, in this skull, has completely merged with the 
premaxillary and frontal of the same side, so that all traces of its 
original borders are obliterated, and it has become thoroughly 
incorporated in the conformation of the osseous superior mandible. 
We will now turn to the underside of the skull of Trogon mexi- 
canus, where we find many points of interest presented for exami- 
nation. Approximately speaking, the majority of structures 
observable upon this aspect are found in the same horizontal 
plane, which plane nearly includes the entire foramen magnum, 
and the anterior moiety of this opening may be said to lie 
in it. 
The roof of the anterior half of the mouth is composed of a 
continuous plate of bone contributed by that portion ot the pre- 
maxillaries. Into the hinder border of this plate we find the 
anterior and dilated ends of the palatines merging. At this 
point these latter bones are quite close together ; posterior to it, 
however, an oval, longitudinal interpalatine space occurs through 
which we can see the osseous nasal septum and the vomer. 
