THE QUADRATE BONE IN BIRDS. 17 
The quadrate is exceedingly peculiar. The neck of the bone is unusually 
long and slender, and is terminated by a round capitulum, representing apparently* 
not the undivided head of the Ratite, but the outer or squamosal capitulum of 
other birds. The inner or prootic capitulum is almost aborted, and is represented 
only by a roughened facet some way down the neck of the bone. The anterior 
process is long and narrow. The quadrato-jugal cup is quite imperfect, and is 
represented by an irregular notch cut out of the postero-inferior angle of the bone. 
The pterygoid condyle is not separate from the mass of bone below. The articular 
surface is peculiar, and consists of a single oblique trochlear surface. 
In the condition of the quadrato-jugal cup and the pterygoid process we have 
features which we have regarded as distinctly archaic; but the degenerate inner 
eapitula and the peculiar mandibular articulation seem to be acquired features. 
This quadrate gives us no help in deducing the relationship of the Fowls to any of 
the foregoing groups. 
VI.—PErRISTEROMORPH. 
Fig. 32. CoLuMBA PALUMBUS. 
In the Common Pigeon the neck of the quadrate is moderately long, and © 
directed somewhat backwards. The capitula are distinct and separate. The 
anterior process is rather long, broad, and pointed. The quadrato-jugal cup is 
very small but neatly formed, and placed quite at the postero-inferior angle. The 
pterygoid process is confluent with the mass of bone below. The mandibular 
articulation is similar to, but even less perfect than that of the Fowl. The two 
last characters are manifestly points of affinity with the Alectoromorphe. 
Fig. 33. PTEROCLES ARENARIUS. 
In the Sandgrouse the capitula are distinct and widely separate, and the neck 
has a backward inclination even more marked than in the Pigeon. The anterior 
process is moderately large, and the body of the bone below is curiously narrow. 
The quadrato-jugal cup is small, well-formed, and low down. The pterygoid 
process is more distinct than in Columba. The mandibular articulation is almost 
normal, with a slightly unusual antero-posterior extension of its anterior part. In 
* See Parker, Skull of Fowl, Phil. Trans., Vol. 159, p. 798. 1870. 
