136 
Annals or the Transvaal Museum. 
For the original position between 
the pterygoids : 
1. The present position of the 
layer. 
2. The presence of the teeth. 
3. The layer apparently does not 
occupy a greater surface than 
the pterygoidal vacuities, i.e. 
no elements of the layer have 
been found on the pterygoids 
or the basisphenoid. 
4. The right side of the layer is 
parallel to the concave inner 
side of the right pterygoid and 
prevomer. 
5. The elements do not occur in 
rows, which is usual in dermal 
armour. 
6. The probability that the layer 
formed part of the palatal sur- 
face is strengthened by the fact 
that the hyo-branchial skeleton, 
the dentary, the complementary 
and all the bones of the skull- 
base and palate, except the 
parasphenoid, were covered 
with teeth. 
7. That the parasphenoid is not 
covered with teeth may be ex- 
plained by the presence of the 
layer of ossifications, which 
passed over its lower surface. 
For dermal armour : 
1. Dermal armour is already known 
between the rami of the jaw, 
but teeth without real skeletal 
support have never yet been 
found in the Stegocephalia , 
although they are known in 
Teleostei and in Selachii. 
2. The left side of the layer is very 
irregular and elements occur 
far below the general surface 
of the ossifications. If the 
layer was pressed into its 
present position, these were 
left behind through meeting 
greater resistance. 
The Vertebral Column. 
The vertebrae are typically temnospondylous and of the rhachitomous 
type. The exact number ot‘ presacral vertebrae could not be ascertained 
in our specimens. Twenty-six were counted, but there is still room 
for at least a few more between the last lumbar and the sacral vertebra ; 
also the connection between the last cervical vertebra and the skull is 
missing, so that the total number of presacral vertebrae will at least be 
thirty. 
The hypocentrum is a latero-symmetrical bone of horse-shoe shape, 
resembling very much the same element figured of Actinodon and 
Trimerorhachis. Seen from the side, its hinder border is more slanting 
than the front one. Its inner surface is rough, and has probably been 
covered by cartilage. The outer surface of the hypocentrum is not so 
prominently keeled as that of Trimerorhachis. Many of the hypocentra, 
especially those near the pelvis (PL XVII and XIX, fig. 2), show a series of 
longitudinal ridges of which generally one on either side of the middle 
line are more conspicuous. There is also a middle ridge, which at most 
attains the height of the lateral ones. These ridges are separated by 
narrow grooves of the same breadth as the ridges. In some hypocentra it 
could be shown that the surface in the grooves, as in Trimerorhachis , 
shows a more conspicuous net-like structure than on the ridges. Whereas 
