1032 MR. D. M. S. WATSON ON 
Gorgonops is really composed of a pair of prevomers fused, just as 
is the rather similar bone in the Anomodonts. 
In the type-specimen of Gorgonops it seems clear that there is 
no median suture down the palate between the posterior nares and 
the very small interpterygoid vacuity. On the other hand, there 
seems to be very indefinite sutures along the side walls of the 
median groove of the palate, exactly in the position where the 
sutures between the vomer and palatines and pterygoids lie in 
Diademodon. 
Tf this: be so then Gorgonops will have a large mammalian 
vomer in the posterior part of its palate and a fused pair of pre- 
vomers anteriorly. 
In Aretops, which is much more primitive than Gorgonops, 
there is some evidence suggesting that the pterygoids reached 
forward to the prevomers. 
Comparison of the series of characters recorded above as 
features of the Gorgonopsid palate with the similar series on 
p- 1022 of this paper referring to Lauria, will show that Lauria 
differs in its palate in exactly the same manner from Gorgonops 
as it does from Diademodon. 
In fact the Gorgonopsid palate, as I have previously pointed 
out, presents a very close resemblance to that of the Cynognathids, 
a resemblance which is much more striking in the advanced 
Arctognathus than in the more primitive Gorgonops. 
If the interpretation of the structure of the palate of Gorgonops 
given above be correct, then the only differences between it and 
that of a Cynognathid are the development of a secondary palate, 
the beginnings of which are seen in that type, and the concurrent 
reduction of the prevomers; a change which is paralleled in 
Crocodiles. 
Amongst the other characters, of which a progressive and 
orthogenetic change is seen in this series of skulls, are the occiput 
and the temporal region. 
The occiput of Arctops (text-fig. 3C) is very nearly flat, with 
a minute foramen magnum and only very slight projecting ridges 
formed by the tabulares and squamosals. It only differs from 
that of the Deinocephalian Z%itanosuchus in the slightly greater 
spread of the squamosals. In particular, it resembles this animal 
in the very great breadth of the interparietal. 
In Scymnognathus (text-fig. 3 B) the occiput is deeply concave 
and the squamosals very wide. The interparietal is very much 
narrower than in Arctops. 
In Diademodon (text-fig. 3 A) the occiput is very concave and the 
interparietal narrow. This form, however, differs pronouncedly 
from the Gorgonopsids in its very largely developed squamosals, 
a feature not shown in the Nythosaurians which seem to be 
related to it. 
In the temporal region Arctops is remarkable amongst Gorgon- 
opsids for the extraordinary width of the parietal region and the 
