MAMMAL-LIKE REPTILES, 759 
the body of the quadrate, there is a step which may (R. 3596) be 
for the outer end of the extremely massive stapes. 
The posterior end of the pterygoid is lightly applied to and 
probably usually fused with the lower end of the basisphenoid at 
the side of the parasphenoid. From the side of the bone in this 
region (49385) a small process is given off which curves round so 
as to shield the front of the fenestra ovalis. From this process a 
slender rod rises very high in the skull with its posterior edge 
nearly in contact with the front of the prootic: although not 
separated by visible suture it is probable that this bone is the 
epipterygoid. In R. 3594 there is a small fragment in contact 
with the parietal in the region of the hinder end of the ethmoid 
which may be the upper end of this bone. 
From its articulation with the basiphenoid the pterygoid passes 
forwards and outwards; the outer wing is the quadrate ramus, 
which on account of the remarkable form of the skull and the 
forward throw of the quadrate, forms a nearly flat, horizontally 
placed sheet of bone overlapping the posterior surface of the 
quadrate. In front of this the pterygoid narrows and then rather 
suddenly widens and passes outwards to the transverse bone. 
Much of the anterior border is in contact with the palatine in 
a straight suture, but there is in 49385 a small medial process 
which extends forwards to touch the prevomer. 
The dorsal surface of the anterior part of the pterygoid is 
produced into a high flange rising in contact with its fellow 
(with which it may be fused, 49385) as a median septum in the 
facial part of the skull. 
The transverse bone (TR.) is separated from the pterygoid by 
incomplete but quite definite and certain sutures on both sides 
of R. 3594. It unites with the pterygoid to form a low flange 
against the side of the lower jaw, and runs outwards, having a 
long suture with the palatine in front to the maxilla and jugal. 
Where the maxilla, palatine, and transverse meet there is 
apparently a very small suborbital fossa only about °5 em. in 
diameter. 
The palatine (PAt.) is a bone of medium size which has a suture 
with the transverse and pterygoid posteriorly, with the pterygoid 
and prevomer medially; its anterior border forms a good deal of 
the posterior naris and its outer edge has a long suture with the 
maxilla. 
The prevomer (PR.V.) is a rather remarkable bone. Behind it 
has a suture with the palatine, for some distance its medial surface 
is separated from that of its fellow by the thin vertical plate made 
by the pterygoids. Further forward the two bones meet in the 
middle line, and from this point forwards their upper surface isto a 
variable extent overlapped by special processes of the premaxille. 
The outer edge of the prevomer forms the whole of the inner 
margin of the posterior naris. From the upper margin of the 
bone a thin flange rises which leans inwards till its upper edge 
touches that of the septum formed by the pterygoids. This flange 
