On some Upper Beaufort Therapsida. 
301 
which forms the entrance to a short duct running through the bone whose 
posterior end opens into the orbit. 
The other bones of the face and of the top of the skull are very similar 
to those of Cynognathus platyceps, and their shapes and relationships are 
adequately displayed in the figure. 
" Vomer" — In section anterior to the orbit the vomer is broad, thin, 
slightly concave downwards, with a ventral median keel and a dorsal median 
groove flanked by thin upstanding walls. When traced forward in longi- 
tudinal section the horizontal plate gradually disappears, the vertical plate 
becomes higher and its ventral por- 
tion swells, so that at the anterior 
end, between the palatine processes 
of the premaxillae, the median plate is 
sharp-pointed above and rounded 
below. At the anterior end the 
bone-mass is certainly single ; along 
its length there may possibly be a 
suture separating an upper portion 
from a lower ; but the median sep- 
tum, except in its lower swollen por- 
tion, is very thin and much cracked, 
so that it is not possible to be absol- 
utely certain of the presence of a 
suture. If a suture is present, then 
the bone between the premaxillse is 
the vomer, and the bone which roofs 
the pharynx is the parasphenoid ; or 
the former is the fused prevomers and the latter the vomer. It is certain 
that the bone which roofs the pharynx forms the upper part of the 
median septum at least ; and that the condition is different from that 
figured by Broom in Diademodon, in that no mesethmoid forms the upper 
part of the septum. On the other hand, if the bone is single, the changes 
which take place in it when traced forward from the pharynx are the 
gradual loss of the horizontal septa, the thickening of the ventral part of 
the vertical plate, and the complete or almost complete fusion of the walls 
of the dorsal groove. 
Posterior to the line of fracture in front of the orbits, the " vomer " 
becomes more arched with a ventral median keel and passes rapidly down- 
wards and backwards, forming the front part of the groove in the palate ; 
the hinder portion of this groove is formed by the pterygoids. Broom and 
Watson have both figured this region in Diademodon, and have shown the 
vomer as forming the whole of this vaulted area of the palate, and Watson 
Cynidiognathus longiceps. — Htn. 
Irregular section across snout. Dorsal 
view. Left septomaxilla not preserved. 
