THE SKULL OF PALEORHINUS L277 
process which forms the posterior half of the upper margin of the 
antorbital vacuity and excludes the prefrontal from this opening. 
The lachrymal enters into and forms the greater part of a depressed 
area which lies behind the antorbital vacuity and extends almost to 
the orbit, leaving only a narrow bar elevated to form the lower anterior 
margin of the orbit. 
Parietals—Behind the frontals the parietals form the posterior 
portion of the cranial roof. They unite with the frontals by trans- 
verse sutures and are here narrow, but after widening gradually for 
about five-eighths of an inch they suddenly broaden to twice their 
anterior width and so continue, until they reach the anterior extrem- 
ities of the supratemporal fossee. They form the anterior one-half 
of the inner boundaries of these fossee and here meet the squamosals 
in sutures which slant backward for some distance and then pass 
transversely to the edges of the median notch, along which they slope 
posteriorly so that on the under surface the parietals extend back- 
ward as thin narrow plates under the squamosals to within one-half 
inch of the posterior margins of these bones. ‘That part of the parie- 
tal which borders the supratemporal fossa on its inner margin is 
deflected steeply downward and outward, leaving a long, oblique 
depression of triangular cross-section, in the outer wall of which the 
fossa is excavated. At a point a little more than one-half the dis- 
tance from their anterior to their posterior margins the parietals 
separate and diverge widely, leaving a broad, rather deep, trian- 
gular recess which is bounded behind the parietals by the squamosals. 
This notch opens very gradually during the first one-half inch of its 
length, and then widens much more rapidly to the posterior margin 
of the skull. It is floored in its anterior part by the supraoccipital, 
and here the parietals nearly completely arch it over from side to side. 
Jugal.—Behind the lachrymal and the maxilla lies the very irreg- 
ularly shaped jugal. Its suture with the quadratojugal is exposed 
as a long curved line sloping diagonally backward and downward 
from the lower posterior angle of the lateral temporal vacuity almost 
to the point of the jaw. The posterior part of this element thus 
appears as a long, slender, wing-shaped extension forming the margin 
of the jaw. Anteriorly the bone widens, forms the cheek between the 
lateral temporal fossa and the margin of the skull and curves upward 
