A FOSSIL REPTILE. (avi 
side-wall of the foramen magnum, and its upper end is in contact 
with the supraoccipital. 
The opisthotic is a large and powerful bone. Its inner end 
was largely cartilaginous, and its ossified part does not touch the 
basis craniil. Part of its posterior face is covered by the ex- 
occipital, lateral to which it forms the very deep and massive 
paroccipital process, the distal upper corner of which is connected 
with the tabulare. The front of the paroccipital process is 
covered by the pro-otic, and the two bones combine to form a 
rounded groove on the lower surface in which the stapes lies. 
The pro-otic is applied to the anterior face of the opisthotic, 
and resembles that bone in having a largely cartilaginous inner 
end. This is, however, larger in area and is clearly pierced by a 
foramen, or possibly two, for the VIIthand VIIIth nerves. On 
the inner side of the skull the inner ear is widely open and lies 
high in the side-wall of the brain-cavity. The whole condition is 
extremely like that in a tortoise. The front edge of the pro-otic 
has a large incisura for the trigeminus, below which is a pro- 
minent process. The fenestra ovalis is a very large irregular 
hole in the bony skull. 
Text-figure 2. 
ja 
EZ Zi) = 
Procolophon trigoniceps. 
A. Posterior aspect of skull. 1. 
B. Right lateral aspect of skull. X 1. 
Composite figures from three perfect skulls. 
The supraoccipital is a very delicate bone, whose inner aspect is 
not known; externally it is exactly like that of a lizard, touching 
the parietals by a very small point, if at all directly. 
The stapes is a relatively thick rod, whose outer end is expanded 
into a plate. 
There is a slender epipterygoid, which expands below and is 
broadly fastened on to the outer surface of the pterygoid just 
