TAG. MR. D. M. S. WATSON ON 
a cleithrum, a screw-shaped glenoid cavity, and a fifth carpal. 
‘A blood relationship between Procolophon and Pariasaurus is 
more probable than one between Procolophon and Labidosaurus, 
despite the very different specialisation of the two types. 
Diadectes resembles Procolophon in its large otic notch, and 
apparently, to some extent, in the features of the cranial cavity. 
It differs, however, in the complete closure of the post-temporal 
fossee by a union of the widened supraoccipital with the tabulares 
and postparietals. In addition to these phylogenetically im- 
portant differences are many due to the very much less advanced 
nature of the type. 
Limnoscelis differs in the apparent obliteration of the otic 
notch and in its closed post-temporal fossz, in addition to the 
retention of many primitive structures. 
The work of Boulenger and v. Huene has shown the very 
great resemblance between Telerpeton and Procolophon, and I 
have been able to confirm their accounts on a magnificent new 
skeleton of the latter lent to me by Mr. Taylor of Llanbryde. 
Dr. Broom, when he first examined Procolophon, expressed 
his opinion that whilst technically a Cotylosaur it was really a 
primitive “ Diaptosaurian,” picking Paleohatteria as perhaps its 
nearest known relative. This choice was rather an unfortunate 
one, for it now seems almost certain that Paleohatteria is really 
a Therapsid. 
This suggestion was, in fact, really founded on such features as 
the digital formula and the presetice of abdominal ribs, which 
have proved to be common to all early reptiles. At the same 
time, the structure of the neural part of the skull does recall 
very strongly that of Sphenodon, or, so far as the interior of the 
cranial cavity is concerned, a Tortoise. 
As I believe very strongly in the value of this part of the 
skeleton as an indicator of affinities, I think it probable that 
Procolophon has some real relationship to the unknown group of 
Cotylosaurs from which these two very diverse forms of reptiles 
sprung. I have carefully examined the skeleton of Procolophon 
in this connection, but can find no other resemblances between 
it and the more modern reptiles which are not also common to 
many other early forms. In particular the glenoid cavity seems 
incapable of having given rise to that of reptiles with a single 
coracoidal element, being curiously advanced in a different 
direction. 
For the opportunity of collecting the material on which this 
paper is based, I am indebted to the assistance of the Percy 
Sladen Trustees, and to G. W. Crozier, Esq., of Donnybrook, 
W. Southey, Esq., of Tentergate, and P. Goosen, Esq., of Haslop 
Hill, S. Africa, without whose hospitality and interest I could 
have done nothing. 
The beautiful preparation of the male skeleton was made by 
Mr. R. Hall, of the British Museum. 
