THE SKULL OF PALEORHINUS 129 
trates the skull margin for an inch. The quadrate also assists in 
bounding this notch, not only on its outer side, whose entire margin 
it forms, but also on its forward end and on about one-third of its 
inner border. Immediately above and in front of this notch the 
squamosal is hollowed out somewhat to form the opening of the otic 
capsule, which is also set into the quadrate to about an equal extent. 
Quadrate.—This element, from being rather narrow above, 
widens considerably below and on its lower margin is thickened to 
form the articulation with the lower jaw. Besides being sculptured 
on the posterior margin for the reception of the otic capsule and the 
notch as described above, the quadrate also partially encloses on its 
anterior margin the quadrate foramen, which pierces the side of the 
skull slightly above the middle of the length of the quadrate, and is 
bounded anteriorly by the quadrato-jugal. The quadrate extends 
on to the lower side of the skull for a short distance and unites 
with the broad posterior wing of the pterygoid and with the lateral 
process of the exoccipital along its anterior surface. 
Quadratojugal.—The quadratojugal unites below the quadrate 
foramen with the quadrate in a large squamous suture which lies in 
the plane of the quadrato-jugal and at right angles to that of the 
quadrate. A buttress from the quadrate increases the sutural sur- 
face and strengthens the union. The quadratojugal is a thin flat- 
tened bone. It is almost entirely excluded from the margin of the 
jaw by the slender extension of the jugal. It reaches the edge just 
at the point of the jaw and forms about an inch of the margin in this 
region, although most of this distance is shared with the quadrate. 
Its upper anterior portion forms the lower posterior margin of the 
lateral temporal vacuity for about one inch, but is excluded from the 
margin above by the squamosal. 
The posterior margin of the bone is excavated to some depth at 
about its middle to assist in forming the quadrate foramen, above 
which the bone again unites with the quadrate. 
OPENINGS OF THE SKULL 
Nares.—As has been said the nares are situated far backward. 
In fact they are more than half-way from the anterior to the posterior 
extremities of the skull, as the distance from the end of the snout to the 
