THE SKULL OF PALEORHINUS 131 
of the lachrymal, and the upper margin of the maxilla in its vicinity 
is also depressed to form its wall. 
Orbits.—One inch behind the antorbitals are the orbits. These 
are considerably smaller than the antorbital vacuities, as their greatest 
length is two and three-eighths inches, while their width is one and 
five-eighths inches. The aspect is upward and outward. The outline 
is ovoid, with the smaller curve anterior, and the axis points slightly 
outward and downward. The frontal forms the upper median border, 
the prefrontal extends thence forward almost to the anterior limit, 
and the lachrymal contains the narrow curve of the extremity and 
extends along about one-third of the outer margin. Behind this the 
upper limb of the jugal enters into the border for another third of its 
length and meets on the narrow bar between orbit and lateral temporal 
fossa with the postorbital, which completes the margin to the posterior 
extremity. From here the postfrontal completes the circuit. The 
bones forming the inner border of the orbit are turned upward along 
their margins and form a thickened wall elevating the orbit and giving 
it a more outward aspect. 
Lateral temporal jossa.—The upper line of the lateral temporal 
fossa lies about behind the middle of the orbit and the cavity extends 
forward and downward at an angle of about 45° with the axis of the 
skull to a point almost opposite the shorter axis of the orbit. It is 
subquadrangular in outline, but the upper posterior angle is extended 
into a tongue-like embayment which is excavated into the squamosal 
for a short distance. The length of the fossa is three inches and its 
width one and three-fourths inches. 
The anterior and posterior walls are practically straight and 
nearly parallel, with a slight divergence, especially at the lower end. 
The lower margin is slightly concave and its general trend is about 
at right angles to the lateral margins. 
The upper margin is formed in part by the squamosal, which 
extends above the vacuity as a bar about three-fourths inch wide. 
Anteriorly this unites with the postorbital and each makes up about 
one-half of the arch. ‘The postorbital also extends around in front 
of the fossa and unites with the jugal to form the narrow bar separating 
the vacuity from the orbit. ‘The jugal also forms the entire lower 
border to the point where it begins to rise to the posterior margin. 
