1903. ] OSTEOLOGY OF THE CUCULIFORMES. 261 
Cuculi, is triangular ; but it differs from the Cuculine plate in that 
it is somewhat swollen, a feature which is especially well-marked 
in Schizorhis. The two sides of the triangle are produced hack- 
wards over the paroccipital notch to join the lateral occipital wing 
of the tympanic cavity: thus they come to project beyond the 
base of the triangle, though they are less conspicuous than in 
some of the Cuculi. There is a barely perceptible precondylar 
fossa. 
The Lateral Aspect of the Cranium. 
The tympanic cavity is oval or oblong in form and of moderate 
size. It is bounded in front by the quadrate, behind by the 
lateral occipital tympanic wing, below by the basitemporal plate, 
and above by the squamosal prominence and by the head of the 
quadrate. 
Within the mouth of this cavity lie several smaller apertures. 
The largest of these is that of the recessus tympanicus anterior. 
Immediately below this is the mouth of the Eustachian tube. 
The foramen ovale and foramen rotundum, three foramina of the 
sinus petrosus, and the mouth of the posterior tympanic recess 
open into the cavity by a common aperture—the fenestral recess— 
which is very small, and lies mesiad of the articular surface for 
the otic head of the quadrate. The mouth of the posterior 
tympanic recess is completely concealed, and can only be made 
out by cutting away its outer wall and passing a bristle through 
from its cavity into the common aperture of the foramina in 
question. In some birds, e. g. Malco, the posterior tympanic recess 
communicates with the tympanic cavity by two apertures—one 
caudad of the foramina ovale and rotundum, and lying within the 
fenestra through which these are approached ; and the other external 
to this fenestra, separated therefrom by a bony column, and lying 
immediately beneath the articular surface for the otic head of the 
quadrate. This external apertwre is wanting in the Cuculitormes. 
Immediately above the head of the quadrate, and between the otic 
and squamosal heads, will be found the aperture of the superior 
tympanic recess, which is reduced in this group to extremely small 
dimensions. The foramen of the 7th (facial nerve) opens also into 
the tympanic cavity between the otic articular surface for the 
quadrate and the rim of the anterior tympanic recess. 
The squamosal and otic articular surfaces for the quadrate form 
a dumbbell-shaped area immediately in front of the aperture of 
the superior tympanic cavity. The actual articular surfaces are 
formed by the expanded ends of the dumbbell only. Where the 
pneumatic area is very large, as in the Striges and Falconiformes 
for example, it breaks through the connecting portion of these two 
articular surfaces so that they become quite isolated, 
The Squamosal Prominence.—The size of this prominence 
depends largely upon the development of the temporal fossa, 
When this is deep the prominence is large; but when shallow the 
prominence is quite inconspicuous. Its anterior angle is produced 
