Annals of the Transvaal Museum. 
213 
It is still free here, but only a very small distance backwards it 
coalesces with the prearticular, and then the two bones cannot be 
separated any more (figs. 8, 10). The suture of this coalesced bone 
with the angular can be traced till the end of the last. The hinder 
portion of this suture is very complicated (figs. 11, 12). Here two 
ridges are developed by both elements. The outer ridge of the 
coalesced prearticular is situated between the two ridges of the angular, 
while the inner ridge of the angular fits in between the two of the 
coalesced bone. These ridges become less prominent forwards, except 
the outer ridge of the angular, which passes into the high vertical side 
of the inner portion of this bone. 
The articulation surface of the coalesced articular has a high 
front margin, which passes into the uppermost of the already mentioned 
two ridges on the outer border (fig. 5). This upper ridge passes in its 
turn into a high back margin, which crosses the upper surface of 
the coalesced bone from the outer border inwards and backwards 
(fig. T). This margin is still visible on the inner surface till just 
below the inner process (fig. 6). 
There is a process from the inner surface of the bone at about 
equal distances from the upper and lower border. Its longest dimension 
is parallel with the larger articulation surface. Its upper surface is 
convex, and forms part of the articulation surface. The lower surface 
of this process is slightly concave at the back, and its free edge is 
sharp (figs. 2, 6, 11, 12). 
The coalesced bone forms another process downwards, being the 
extreme end of the ramus. This process has a triangular section, of 
which the outer angle is the most acute (figs. 5, 6, 7). 
The articulation surface consists of three parts : an upper surface, 
a vertical surface, and the upper surface of the inner process (figs. 
7, 11, 12). The upper and vertical surfaces meet in a ridge, which is 
convex upwards and inwards. The angle between the upper and 
vertical surfaces is acute ; the one between the vertical surface and the 
upper surface of the inner process is right. 
The upper surface is convex in a backwards- forwards direction, 
and concave from the outer to the inner edge. The vertical surface 
is convex inwards. 
The prearticular continues forwards from the hinder border of 
the inner opening of the vacuity in the jaw, forming the whole lower 
border of this opening, and then disappearing behind the opercular 
(figs. 2, 10, 13, 14, 15, 16). It has been followed behind this element 
till above the place where the angular disappears between the opercular 
and the dentary. Before reaching the opercular it is in touch with 
that part of the dentary which might be allocated to the lower end of 
the complementary. 
A ridge runs near and parallel to the lower border of the bone on 
its outer surface (in the Meckelian cavity, fig. 10). The height of 
this ridge increases towards the back, and it also rests there on a ridge 
of the angular, which on this element runs parallel with and a little 
above the lower border. The suture of the angular with the coalesced 
part of the prearticular has already been described (figs. 11, 12). 
The articular is still a separate bone directly behind the inner 
opening of the vacuity of the jaw. Just a few millimetres further 
backwards it coalesces with the prearticular. The exact relation of 
the two parts is thereby totally obliterated, but it is still possible to 
