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Annals of the Transvaal Museum. 
behind. They apparently represent a new dentition and are ready to take 
the place of the adjoining large tooth. 
The large tooth near the hinder end of the choana has also a 
labyrinthodont structure. 
The small teeth on the complementary, the prevomer, the pterygoid, 
and the basisphenoid are all of the same kind. They have a sharp- 
pointed conical shape and in horizontal section they are circular. On the 
pterygoid their size seems to vary with the place of occurrence, but this does 
not seem to be the case on the basisphenoid or the complementary. The 
largest teeth visible on the pterygoid occur near the outer border of the 
pterygoidal vacuities and near the front end of the infra-temporal fossa. 
Between these patches of larger teeth there are numerous smaller ones, 
which continue backwards and also cover the basisphenoid. Excepting 
the extreme border of the pterygoidal vacuities, the teeth on the front end 
of the pterygoids are unknown. Those near the junction of the palatine 
and the prevomer are of the larger type. The zone of larger teeth on the 
pterygoid shown in fig. 1 of the preliminary description [is not so strongly 
marked as may be inferred from the drawing. 
The structure of these small teeth bears a labyrinthodont character. 
The extreme end of the tooth is smooth ; below this the outer surface is 
covered with very fine ridges, parallel to the axis of the tooth ; the lower 
half of the outer surface is covered with grooves parallel to the tooth-axis. 
The pulp-cavity of these small teeth is also filled with calcite. The calcite 
cone is much shorter than the tooth. When the tooth has broken off very 
near to its base, plications of the surrounding tooth-substance are seen to 
enter the calcite cone. These plications, however, do not penetrate very 
far into the calcite. 
There still remains to be described a very remarkable feature of the 
skull of Myriodon. Both skulls show a mosaic of small, irregular, and 
flat ossifications in the pterygoidal vacuities. This mosaic forms a 
tolerably fiat layer, which however, is not situated in the plane of the 
pterygoidal edges. At its hinder end its position is higher than the lower 
surface of the pterygoids immediately on the outer side of the sutures 
with the basisphenoid. This is due to the fact that the pterygoids, in 
passing outwards from the suture with the basisphenoid, bend slightly 
downwards until they reach the middle of the hinder end of the ptery- 
goidal vacuities. From this point they turn slightly upwards. The 
middle of the hinder end of the flat layer of ossifications passes below the 
hinder end of the parasphenoid and is therefore lower than the palatal 
surface of the basisphenoid. The sides and front end of the layer of 
ossifications are situated much lower than the inner borders of the ptery- 
goids and the hinder borders of the prevomers. The distance from the 
lower surface of the parasphenoid in front to the upper surface of the 
bony layer is 12 mm. The distance from the hinder border of the right 
prevomer to the same surface of the ossifications is 9 mm. 
The hinder border of the layer of ossifications is notched. The notch 
is very broad and short. Through this notch the hinder end of the layer 
consists of two processes, which project into the hinder ends of the 
pterygoidal vacuities. There is still some distance between the hinder 
border of the layer and the front edge of the pterygoids. The right side 
of the layer is clearly visible. It lies at a uniform distance of about one 
centimetre from the concave inner border of the pterygoid and prevomer, 
