AND CLASSIFICATION OF THE FOSSIL REPTILIA. 
271 
angular bend to the right, followed bj a similar angular bend to the left. The trans¬ 
verse width of each bone posterioidy is 1 centim. to the position where it is overla})ped 
on the posterior corner by the epi-otic bone, but it becomes wider anteriorly, since it 
extends into the posterior corner of the orbital vacuity, where the width is half as much 
again. The extreme antero-posterior measurement in the median line is 1'4 centim. 
There appears to be a small ossification between the posterior angle of these bones 
on the inclined occipital surface which may be the inter-parietal. Laterally, the 
parietal meets three bones, of which the most posterior is (1) the epi-otic, which rests 
upon the parietal; and (2) the scpiamosal, which is in contact with (3) the post-orbital. 
Anteriorly, the parietal is in contact with the frontal and post-frontal bones, and 
there is no evidence of division in tlie part of the parietal in front of the foramen. 
The occipital surface of the skull is not seen. 
The frontal bones are a pair of flat oblong bones, almost as long as the orbito¬ 
temporal vacuity, divaricating a little posteriorly, and narrower in front. The median 
suture between them is undulating, 1'7 centim. long. The lateral branches of the 
bones extend outward and backward above the orbits, about as far as the middle of 
the parietal foramen ; their posterior contour is concave, and the transverse width 
over the posterior angles is 1’4 centim. The extreme length of the frontal is 
2T centime. The width of the bones diminishes anteriorly, by the wavy external 
borders converging to half a centimetre. Tlie width in the narrow space where their 
borders enter into the orbits is 9 millims. 
External to the posterior border of the frontal and partly overlapping the parietal, 
is a long narrow bone, I'l centim. long, pointed in front, and widening to 2 millims. 
posteriorly, wbich I regard as the post-frontal. There is no indication that it has any 
other relations than v/ith those two bones. 
Extending along the anterior border of the frontal is a sub-triangular bone, which 
widens as it extends forward, which is the pre-frontal. It is 1 centim. long, extends as 
far forward as the frontal, and is 7 or 8 millims. wide, wedged between the frontal and 
lachrymal, and meeting the nasal. In front of the frontal and pre-frontal are the 
nasal bones, which, owing to the state of preservation, are imperfectly defined. The 
suture is seen, by which they unite laterally with the maxillary bones, and there are 
indications of the median suture, so that they cover the superior convex pre-orbital 
area. Each is more than 1 centim. wide posteriorly and (as the extremity of the 
snout is lost) fully 1'5 centim. long. 
The post-orbital arch commences with the large sub-triangular bone whose ex¬ 
tremity forms on each side the lateral posterior angle of the skull. The surface of the 
bone is convex from front to back, and its angular extremity is inclined downward, 
outward, and backward. It rests by squamous overlap upon the posterior border 
of the squamosal and the external surface of the parietal. Its relative size is 
comparable with the same bone in Labyrinthodonts, and is much greater than in 
Pareiasaurus, and altogether more conspicuous than in Dicynodonts, which usually 
