SKULL OF A PARIASAURIAN REPTILE. Wyil 
it includes such types as Seymouria, Diadectes, Procolophon, 
Captorhinus, Pariotichus and Pantylus. ‘These reptiles are 
extraordinarily different in many features, and those in which 
they agree are essentially primitive characters which they share 
with Temnospondylous Stegocephalia. 
The group is in fact only held together by the following 
character, which separates it from other reptiles :— 
The skull is completely roofed in the temporal region ; every 
other feature in the skeleton can be matched in some or other 
early reptile. 
Cotylosaurs are distinguished from the Temnospondylous 
Amphibia solely by the facts, that the intercentra are reduced and 
the neural arches are expanded and thickened and the zygapo- 
physial articulating faces placed horizontally, and by the presence 
of only two bones in the proximal row of the tarsus (I believe this 
feature does occur in some small Stegocephalia which, as shown 
by the fusion of the hemal arches to the centra in the caudal 
region, are quite unconnected with reptilian ancestry). 
It is quite certain that the Reptilia, as a whole, must have been 
derived from a form with a roofed temporal region, for all known 
Carboniferous amphibia have this feature, and so also have all 
Paleozoic bony fish. Therefore this character, which alone 
separates and holds together the Cotylosaurs, is merely a 
primitive one. Whether all reptiles are derived from a cotylo- 
saurian ancestor is not so certain ; it is conceivable, though I do 
not regard it as at all probable, that some of them might be 
derived from amphibian types which had developed temporal 
vacuities. The fact that quite a number of early reptiles shew 
traces of the broad neural arches and horizontally placed zyga- 
pophysial facettes, which are on the whole the most characteristic 
of all the structures of the post cranial skeleton of Cotylosaurs, 
suggests strongly that these types at any rate, and of course their 
allies, have been derived from reptiles which, if we knew them, 
would be unhesitatingly called Cotylosaurs, 
Seymouria stands apart from all other Cotylosaurs in the 
extraordinarily Stegocephalian appearance of its skull, its 
resemblance that is to the skulls of the majority of Temno- 
spondyls and Stereospondyls, for it does not resemble more 
closely than those of other Cotylosaurs the skulls of the smaller 
Stegocephalia, the Branchiosaurs and “ Microsaurs.” 
This resemblance depends on :— 
1st. The shape of the skull. 
2nd. The narrow otic notch placed high up so that the 
abularia are fairly near to the middle line. 
3rd. The fact that the quadrate slopes backwards so that its 
lower end lies far behind the upper. 
Ath. The upward divection of the opisthotics. 
These four characters are really all connected, the presence of 
any one almost implies the others. 
I do not think there can be much doubt that in these features 
