34 
In lateral aspect it is roughly four-sided in outline, longest, and deeply 
and angularly concave above, and sinuous in front and behind with a 
convergence downward to the comparatively short base which is broadly 
and shallowly concave. 
It consists of a plate-like main portion from which is given off an 
antero-superior alar extension and a postero-superior alar extension directed 
upward and forward and upward and backward respectively. Internally 
the bone is strengthened by two large flanges which are united above and 
diverge downward to opposite ends of the base. 
The alar extensions, or wings, are both broad-based and narrow 
rapidly upward. The posterior one is flat, continues in the plane of the 
main portion of the bone and ends in a slender point. The anterior one 
leaves the general plane of the outer face, the contained external angle 
approaching 130 degrees. It is curved at right angles to its length pre- 
senting a transversely convex surface facing backward and upward, and, 
as the bone is thin,* its lower, front surface is transversely concave. 
Of the internal flanges the posterior one is the larger and the stouter 
of the two. It is carried backward and inward in much the same general 
line of direction as the upper part of the anterior wing, in fact a prolongation 
backward of the superior border of the wing forms the joint apical portion 
of the converging flanges. The more anterior and thinner flange is also 
directed backward but more inward than the larger one, and its inner 
anterior surface is a continuation backward of the inner concavity of the 
anterior wing. The two flanges partition the bone internally into three 
unequal areas; an anterior one, the largest, consisting of the moderately 
shallow, inner concavity of the anterior wing and its backward continuation 
by the anterior flange; a median one, the smallest of the three, deeply 
confined between the upwardly converging flanges; and a posterior one 
deeply but more openly enclosed by the posterior flange and the posterior 
wing. 
The sutural union of the pterygoid with the quadrate is extensive 
and is effected by the application of the external face of the former to the 
inner face of the flange of the latter, the surface of contact on the pterygoid 
extending forward from the full height of its posterior border so as to 
include nearly the whole of the wing area and the lower portion of the bone 
to a short distance in advance of its inferior midlength. The slender 
upper end of the wing reaches up to within a short distance of the head 
of the quadrate, the front border of the wing and that of the flange of the 
quadrate being coincident for some distance down. The posterior border 
of the wing below its slender upper termination comes to a thin edge. 
Below the wing the posterior border thickens to some extent, is rugose 
and is applied to a ridge on the face of the flange of the quadrate. Still 
farther down the postero-inferior angle of the bone becomes stout, is 
roughened, and fits into the narrow concavity between the posterior border 
of the quadrate, where it is angularly most protrudent, and the base of 
the flange. 
The pterygoid meets the maxillary in two small, separate surfaces, 
viz., one, infero-anteriorly where the bone curves outward and forward 
over the lower portion of the posterior end of the maxillary and ends 
pointedly, the other, a short distance higher up, where the anterior margin 
passes forward on the inner side of the posterior process of the maxillary. 
