132 ON A NEW SPECIES OF DICYNODON 
which lies parallel with the longitudinal axis of the skull, and con- 
sequently nearly at right angles with them. Anteriorly this bony 
bar becomes connected with the process which forms the posterior 
boundary of the orbit. The upper wall of the cranium itself is very 
narrow, measuring only 1°3 inch across posteriorly, but it expands 
anteriorly, until, at the level of the posterior margins of the post- 
orbital processes, into which its margins gradually pass, it is 2 inches 
wide, 
The supratemporal fossa, circumscribed by these parts on each 
side, are 3 inches wide by 14 inch long; and while their anterior, 
posterior, and external boundaries are nearly straight, the inner 
boundary, formed by the walls of the cranium proper, is concave. 
The narrow and flattened intertemporal region of the skull ex- 
pands anteriorly into the interorbital region, which has a nearly 
square outline, 3} inches wide by 3 inches long. It is convex 
from before backwards, and exhibits a slight median ridge, which is 
much more marked in the original fragmentary specimen than in that 
figured. 
I have not been able to detect any clear evidence of the existence 
of a parietal foramen in this skull; but in another specimen it is 
situated in the middle of a line drawn from the anterior margin of 
one temporal fossa to that of the other. 
Anteriorly the interorbital space is bounded by two strong con- 
verging ridges (less distinct in this specimen than in others), which 
pass forwards and inwards, to meet in the middle, rather behind a 
line uniting the anterior and inferior margins of the orbits. Here 
they are joined by the low longitudinal ridge which has been stated 
to traverse the interorbital region. 
Ikach of the converging ridges exhibits a thickening rather in- 
ternal to its middle, which is continued for a short distance obliquely 
inwards. 
In front of the orbits the facial bones form a thick mass, produced 
downwards and forwards in the way already described, and which is 
so much wider on its oral than on its nasal side that it may be com- 
pared to a trihedral prism. Transverse sections, however: (figs. 3—6, 
Pl. NXIT. [Plate 8]), show that its outline is not quite so simple as 
that of a trihedral prism would be, its surface being raised into seven 
longitudinal ridges, separated by as many slight excavations. Of 
these ridges one is in the middle line above, while the other threc 
lie on each side. Of these the lowermost, situated in the lower and 
outer part of the mawilla, is very strong and thick, and corresponds 
with the alveolus of the tusk. The middle lateral ridge is thin and 
