An.nals or the Tuans vaal Museum. 
211 
edge between tlie outer and upper surfaces of the border. It rises, 
however, to a high and acute wall, after passing* the broadest part of 
the border, and continues up to the end of the dentary. The hind end 
of the groove between these ridges is situated on the complementary. 
There is a depression on the outer surface of the dentary near the 
symphysis, which accommodates the corresponding canine of the upper 
jaw when the mouth is closed. This depression runs parallel with the 
front surface of the symphysis, and extends from the upper border 
downwards and backwards till near the lower one. The described 
position of this depression seems to me to be the normal one, 
corresponding with a more or less vertical position of the occipital 
plate. When this condition has been complied with the alveolus of 
the canine inclines downwards and forwards under an average angle 
of 45 degrees. To fit into the depression of the lower jaw the end of 
the canine must therefore curve backwards. Those cases where the 
canine passes abruptly over the ridge, dividing the symphysial outer 
surface from the outer surface of the dentary, or which, generally 
speaking, do not comply with the above conditions, must be strongly 
distrusted, for there is every reason to believe that they have suffered 
through fossilization. 
In the upper front part of this depression there is a small ridge, 
parallel to the ridge between the outer surfaces of the symphysis and 
the dentary and separated therefrom by a deep and narrow groove. 
This ridge originates at the upper border and passes downwards to 
near the middle of the depression. The deepest part of the depression 
is situated directly behind this ridge. 
The hind part of the dentary is deeply notched by a vacuity in 
the jaw, the upper projection forming the whole upper border and 
surrounding with the lower projection the fore end of the vacuity. 
The upper border of the vacuity is slightly convex downwards ; the 
fore end strongly concave backwards. The lower projection is the 
shortest, and terminates in a point covering the outside of the angular. 
The upper projection retains the same breadth up to its end at the 
hinder end of the vacuity, where it reaches the visible surface of the 
surangular, just above the upper connection of the two parts of the 
angular. 
The Angular . — This is the first bone following on the dentary on 
the outside. It is already distinguishable in front of the lower end 
of the canine depression on the dentary (fig*. 3). In this region it is 
a very high and thin bone (figs. 14, 16), of which the outer surface is 
covered by the dentary and the inner surface by the opercular. The 
narrow lower border only remains free. The height of the bone 
diminishes quickly backwards and becomes a minimum below the 
centre of the vacuity in the jaw. The outer surface of the angular is 
hollow from this point forwards, thus accommodating the lower projec- 
tion of the dentary (fig. 1). The lower border of the bone is broadest 
where the height is a minimum. The outer surface expands fan-like 
from this point backwards. It forms a narrow process towards the 
hinder end of the upper projection of the dentary, which process there 
broadens into a thin vertical plate. Another process is formed at its 
lower border. This starts in front of the hinder end of the vacuity 
in the jaw, and is united inwardly to the lower border of the inner 
vertical part of the bone. The extreme end of the process is, however, 
