AND CLASSIFICATION OF THE FOSSIL REPTILIA. 
235 
brain-case in the previously-described specimen (Plate 10, fig. 2). The transverse width 
between the vertical anterior borders of these bones exceeds 2 centims. Anterior to 
them, and above them, the median vertical plate extends forward. It is 1‘5 centim. 
wide at its base, which is concave from side to side, straight, and ascends forward and 
upward. At the anterior fracture the plate is over 3 centims. deep, and is formed of 
a pair of lamellar bones, in contact in the median line, wuth concave external sides, so 
that the transverse measurement in the middle is only 6 millims., but they widen 
again superiorly to I'.5 centim. before forming the transverse lateral expansions like the 
cross-piece of a capital T (fig. I). 
These bones, regarded as parietals, are in contact, inferiorly, with a median 
bone behind, which may be the inter-parietal, while the post-parietals, which appear to 
cover them superiorly and posteriorly, seem to terminate at about the anterior 
fracture : but fractures are numerous, a.nd sutures so nearly obliterated, that it is 
difficult to determine the structure with certainty. This interpretation would bring 
the parietal bones into the roof of the cerebral chamber in advance of the inter¬ 
parietal, with a narrow concave surface, from the lateral borders of which bone appears 
to have extended downward, so as to define a vertical vacuity in the median plate, 
thougli the descending processes are broken away. 
The superior surface of the temporal region is divided by a well-marked median 
suture, which becomes wdder posteriorly, and its lateral margins are prolonged back¬ 
ward in a V form to the posterior extremity of the squamosal, though the level of this 
groove is much below that of the external zygomatic bar, from which it is separated 
by a deep narrow depression Avhich extends downward and outward over the convexity 
of the anterior part of the squamosal bone. Tire jDostero-anterior convexity of the 
tsmporal region ascends in vertical position as it extends forward and diminishes in 
transverse breadth, till, at about 4 centims. behind the anterior fracture, it merges in 
the transverse ledge, which extends outward on each side of the median vertical plate, 
and as it curves forward it comes nearer to the superior surface of the skull. Seen 
from above, this temporal region has the sides sub-parallel; the transverse section 
posteriorly is half a circle, about 3^ centims. wide. The width is scarcely diminished 
anteriorly, but the convexity diminishes, until at the anterior fracture it is replaced by 
a slight mediah concavity, and nothing remains of the convexity but the rounded 
margins of the transverse plate, which is less than half a centim. thick at the fracture, 
and has a transverse extension outward of 1 centim. beyond the vertical plate. From 
back to front this superior area is regularly convex, and the contour probably resembled 
that of Dicynodon pardice 2 )s, but behind the convexity there is a slight concavity 
along the outwardly diverging surfaces. It is possible that the anterior extension of 
the inferior part of this brain-case was no greater than in the specimen previously 
described (Plate 10, fig. 2). 
Within the post-occipital basin the remains are exposed of what I regard as an 
extremely thin plate of bone. Its vertical extent, from the side of the axis iqjward, 
2 H 2 
