U4 MR. D. M. S. WATSON ON 
General Discussion. 
That the animals whose structure I have discussed under the 
heading of Tapinocephaloids are all closely allied admits of no 
discussion, and is self-evident in every detail of their structure. 
To the same group belongs the Russian type Dewterosaurus. 
As shown clearly by Eichwald’s figures, the dentition is absolutely 
characteristic, the powerful incisors which interlock are struc- 
turally identical with those of Zapinecephalus. The enlarged 
canine so clearly shown in his figures occurs in the remarkable 
type Lamiasaurus which I have described above, and the presence 
of only a single molar is a variation of slight importance. The 
skull figured by Prof. Seeley has all the characteristic features 
of the group, the broad zygomatic arch with the postorbital 
obviously widely meeting the squamosal and the covering of the 
side of the parietal by the postorbital (as shown and lettered 
““post-frontal ” in Seeley’s figure) being identical with the struc- 
tures in the South African forms. Even the slight difference in 
the narrowness of the intertemporal bar and the erest on the 
parietals can be matched in a fragment from South Africa in 
the British Museum. Seeley’s figure also seems to show that 
there was the very characteristic vertical area of basioccipital 
below the condyle and the large quadrate characteristic of the 
group. 
The Russian type Rhophalodon and that described by Twelve- 
trees as Cliorhizodon orenbergensis (R. 4077), which is perhaps 
generically identical with the previously deseribed Deinosaurus, 
are apparently closely allied to Vitanosuchus. Cliorhizodon (at any 
rate, as shown by the beautifully preserved type-specimen in the 
British Museum) is extraordinarily like a small Zitanosuchus, 
as was, in fact, recognised in the original description. ‘There is 
nothing in the whole structure of the skull to prohibit a 
connection. 
Whether Zitanosuchus is really closely allied to the Tapino- 
cephaloids, or whether it is a specialised Gorgonopsid, as Broom 
now believes, is perhaps more doubtful. It resembles the Tapino- 
cephaloids in the extraordinary thickening of its skull and in the 
whole texture of all the bones. 
The whole structure of the temporal region, the form of the 
squamosal, and the relations of the tabulares (postorbitals, parietals, 
and squamosals) are identical in the two types. The very curious 
auditory groove is the same in each type. The premaxille of 
Trtanosuchus have a thoroughly Tapinocephaloid appearance, and 
the position of the external nares far behind the end of the 
snout on the dorsal surface is unparalleled in Therapsids, except 
in that group. 
If Rhophalodon is indeed related to Titanosuchus, then in the 
large quadrate and the vertical area of basioccipital below the 
condyle we have very striking resemblances to the contemporary 
Tapinocephaloids. 
