104 SHOPELDT. [VoL. lil. 
brain-case seems to be larger in such a species as 7. tyranniis 
than it is in some of the other genera. This feature in them 
all, however, is made to be still more apparent by their great, 
wide, and flat superior osseous mandibles, which constitute such 
a striking character in the skulls of the vast majority of these 
Tyrant Flycatchers. When we come to examine the bony, upper 
beak, in such a form, for instance, as the King-bird (7. tyrannus), 
we find that the external narial apertures are large and sub- 
elliptical in outline, and these, when covered by the thinner 
posterior part of the horny sheath of the mandible, constitute 
the nasal fossz of descriptive ornithologists. It is in the ex- 
treme fore part of either of these that the small subcircular and 
functional nostril opens, while in some species, or certain indi- 
viduals of some species, nearly all this anterior part of the 
rhinal chamber may fill in with bone, in a manner I have already 
described above. A slit, on either side, just in front of the nasal 
bone, remains open (but is always covered with the integumental 
mandibular sheath), and the aforesaid aperture comes to be the 
true outer nostril. In figure 19 I show this condition in a 
specimen of JZ. crinztus, but in another skull before me of JZ. 
cinerascens, very little bone is deposited in these parts, they 
being more like the skull of the Black Phoebe shown in figure 
18. All grades of this condition are to be met with between 
these two extremes. Sometimes a small, curled piece of bone 
remains free, on either side, within the rhinal chamber, and, held 
in place by surrounding structures, resembles a “turbinal bone”’ ; 
and in addition to these, the /acrymat/s remain free in these clama- 
torial birds, being situated, in each case, immediately anterior to 
the pars plana. These I have figured for MZ. crinitus in my 
paper on the Macrochires, in the hands of the Linnzean Society 
of London. 
Flat, and for the most part smooth, the under side of the pre- 
maxillary region of the skull in front is bridged across with a 
thin, bony layer, a condition rarely found among our oscine pas- 
serine birds, except in such species as Setophaga. 
Tyrant Flycatchers, as a rule, have the interorbital septum 
far more perfectly completed in bone than do either the Warblers 
or Thrushes, or the nearest allies of these latter; and in JZ. czne- 
vascens a large foramen exists between the mesethmoid and 
the pars plana, immediately beneath the frontal region of the 
