192 
PROFESSOR H. G. SEELEY ON THE STRUCTURE, ORGANIZATION, 
part of the parietal region which is posterior to the cerebral hemispheres shows, I 
believe, that the cerebellum was relatively narrow and thrust downward in the way 
seen in Birds, Ornithosaurs, and Dinosaurs. The length of the cerebral region is about 
15 millims,, so that the head would be 5§- times as long as the brain. The cerebrum 
may occupy 11 to 12 millims. in length; its width is less evident, but appears to 
have been about 7 millims. The hemispheres were high, and flattened at the sides, 
so that on the whole, in so far as the brain differed from that of an Ornithosaurian, it 
appears to have approximated to that of a Dinosaur. There appears to be a small 
parietal foramen placed far back, and in advance of it there is a slight oblong inflation 
of the cast of the cerebral cavity. I describe in succession the median roof bones of 
the head. 
Supra-occipital .—The supra-occipital region of the skull is imperfectly exposed, 
since only the portion is seen which lies above the occipital foramen. It looks 
obliquely upward and backward. It is defined anteriorly by the occipital crest. 
This crest is in two lateral portions, which meet mesially at about a right angle, and 
diverge outward and backward. The posterior surface of the bone is divided into two 
shallow, lateral, concave areas by a slight sharp median inclined ridge. 
The parietal hones .—The parietal region is greatly compressed from side to side in 
its hinder part, so as to rise into a short sharp parietal crest (now broken away), 
which made the sides of the bone concave from the occipital crest forward. The 
length of this compressed area is only a few millims. On it the small ovate parietal 
foramen appears to be placed. In front the bone is lost, but I think the horizontally 
flattened state of the frontal bone anteriorly, and the comparatively flattened state 
of the mould of the cerebral hemispheres, together with the thinness of the bones, 
justifies a belief that the parietal bones became flattened superiorly as they widened 
and extended forward, and that the parietal crest was moderately elevated. There 
were two parietal bones, and the median longitudinal suture between them is seen as 
an elevated line on the mould beneath, where the bones are lost. The transverse 
suture between the parietal and frontal bones is at a distance of about 12 millims. in 
advance of the median angle of the occipital crest. This suture has a transverse saw¬ 
like edge, and admits the median extremity of the parietal bones to extend slightly 
forward between the hinder margin of the frontal bones. 
The frontal hones .—The frontal bones are double, being united by a median suture. 
They exhibit an oblong surface, which was flattened horizontally. Their anterior 
extremities extend forward between the nasal bones in a V-shape, while the lateral 
parts of this suture diverge forward and outward. Posteriorly, the outer corner of 
the bone on one side is notched out by what appears to be the temporal foss, and, 
although the temporal arcade is not preserved, it may have extended backward from 
the narrow post-frontal process external to the notch in the manner seen in Ornitho¬ 
saurs, Dinosaurs, Nothosaurs, or Anomodonts. The lateral borders of the frontal bones 
are concave, 15 millims. long, and are superior margins of the orbits. They are slightly 
