STUDIES OF THE MACROCHIRES. 
319 
of these two species is of so slight a nature that we cannot 
readily distinguish them; for if a series of each were mixed up 
before me, there would be no difficulty whatever in rapidly 
selecting the skeletons which belong to either of these two 
species. As I proceed with my detailed descriptions, I will 
point out the more marked of these differences, while my obser- 
vations must be considered as applying directly to the skeleton 
of T. mexicanus , unless otherwise specified. 
Of the Skull (PI. XVIII. fig. 8, and PI. XIX.). — Viewing this 
part of the skeleton from above, we find that a stroug transverse 
line separates the superior osseous mandible from the frotito- 
lacrymal region, which latter arches upwards and backwards from 
it. This superior mandibular portion of the bony beak is rather 
low from above downwards, broad at the base, tapering rapidly 
to the tip, while its osseous tomia are sharp, and the culmen is a 
graceful, rounded, and unbroken arch from the frontal region to 
the tip of the beak. The narial apertures at its sides face 
upwards and outwards ; they are large, of an elliptical outline, 
and with smooth, rounded edges. 
Each lacrymal bone is a somewhat slender, peculiarly-shaped 
element of anjAlike form, which freely articulates by its supero- 
mesial surface or moiety with a vertical facet offered by the cor- 
responding frontal. Its upper end rises above the surrounding 
surface of the skull, while its lower extremity fails to reach the 
quadrat o-jugal bar below. 
The region between the orbital peripheries on the superior 
aspect of this skull is very narrow, and presents a shallow longi- 
tudinal furrow. Posterior to this part the parietal region is 
characterized by two laterally placed roundly convexed eminences, 
with a rather better marked median longitudinal track between 
them, being the continuation of the furrow just alluded to in the 
interorbital region. 
Viewing the skull of this Trogon upon its lateral aspect, this 
marked rounding of the parietal region lends to it rather an 
unusual configuration for the cranium among birds. 
Upon this view, too, we must note the rudimentary condition 
of thesphenotic process, while the squamosal apophysis below it is 
large and conspicuous. The interorbital septum, per sc, is entire 
though very thin, while, on the other hand, the foramina at the 
posterior aspect of the orbital cavity are far larger than is required 
for the nerves to which they severally give passage ; especially 
