'Tv- 
22 
Prf 
is most marked toward the front where its downwardly curving front 
margin is conspicuously furrowed in a fore-and-aft direction. The inner 
surface of the pocket is everywhere quite smooth. 
The outer margin of the pocket is formed by the posterior curve of 
the orbital rim. The inner wall of the pocket thickens somewhat to the 
front to form the inner margin which is straight and extends, from a point 
below and in advance of the antero-exterior curve of the supratemporal 
fossa, downward and slightly forward, continuing for a short distance 
below the pocket as a process representing the lower end of the postfrontal 
contribution to the postorbital bar. This inner margin is external to, 
and for the whole of its length to near its upper termination is in contact 
with, the ascending process contributed by the jugal toward the formation 
of the postorbital bar. Postero-inferiorly the rotundity of the postfrontal 
encroaches on and considerably lessens the width of the infratemporal 
fossa in its upper half. 
Prefrontal. {Prf.). Figures 3, 4, 3, 8, 9, 10, and, 11. The prefrontal 
is about 2J times as long as broad, and is broader in its anterior half than 
behind. From being posteriorly in the same horizontal plane with the 
frontal it curves convexly outward and downward 
anteriorly to meet the lachrymal and in so doing 
forms the supero-anterior portion of the orbital 
rim. It is bounded behind by the frontal, on the 
inner side extensively by the nasal, in front by the 
nasal, and below anteriorly for a short distance by 
the lachrymal. It projects backward into the 
frontal bone, narrowing about equally from both 
sides to a point behind. The prefronto-frontal 
suture is sinuous and both bones are here strong 
and thick. In front the prefrontal overlaps the 
downwardly broadened portion of the nasal to 
Figure 9. Ri}?ht prefrontal of a Considerable extent, and descending also over- 
view lachrymal. The anterior end is pointed, 
?)biS(iueiy from behind. F, and downward and backward to the orbit the 
outline is broadly sinuous. In approaching the 
r , pie ron a . orbit from the front the bone curves rapidly out- 
ward convexly to the orbital rim. Its lower surface in front of the orbit, 
at the latter’s supero-anterior curve, is excavated, leaving the* bone thin 
with only a slight strengthening at the orbital rim. This excavation is 
almost circular in oAitline, roughly 55 mm. in diameter, and about 22 mm. 
thick, forming a depression facing downward, inward, and slightly back- 
ward within the orbit in advance of the orbital rim. Externally above 
its midbreadth, and about half-way between its anterior end and the 
orbital rim is a conspicuous foramen which enters the thickness of the 
bone in front of the inner excavation. 
The area of the inferior surface of this bone is only a little over that 
of its superior surface, accounted for by the extent to which it overlaps 
the nasal, lachrymal, and frontal above. Interiorly the prefrontal presents 
a deeply concave surface, facing downward, outward, and backward, 
between the lachrymal in front and the frontal behind. Internally it is 
bounded by the lachrymal for its anterior half-length, and for the remainder 
of the length by the nasal and frontal in nearly equal proportions, the 
contact of the latter, however, being the greater. 
