474 Transactions of the Boyal Society of South Africa. 
conversation I was persuaded rather to leave some things I was doing 
and to pay a flying visit to the American Museum. Through the kindness 
of Professor Osborn and Dr. Matthew I was enabled to examine every- 
thing I wished to see, and I had the further advantage of having Dr. 
Case as a fellow-worker at the Museum. Though Dr. Case was busy 
working at the Cotylosaurs, and had much new material on hand of both 
Cotylosaurs and Pelycosaurs, he most generously allowed me to study any 
of his specimens, and gave me every assistance in his power, including 
information about the specimens in Chicago. To him, to Professor 
Osborn, and to Dr. Matthew is largely due the fact that, though I had 
only a few days in New York, I was enabled to do practically all the work 
I had hoped to do. 
Elsewhere I shall publish the detailed results of my examination of 
the Pelycosaur and Cotylosaur skulls, and in the present paper confine 
myself mainly to the conclusions and their bearing on South African 
problems. 
As the result of the researches of Cope, Baur, and Case, and especially 
of Case, the anatomy of the Pelycosaurs is well known, with the exception 
of only a few points, and of these latter the most important is the struc- 
ture of temporal region. By Baur and Case there are believed to be two 
fenestras, the upper small and the lower large. According to Case's 
interpretation the large fenestra is bounded in front by the post-orbital 
and jugal, and behind by a large triangular bone which he calls the pro- 
squamosal. The small upper fenestra lies between bones which he 
believes to be post-orbital, the parietal, and the quadrato-jugal. The 
squamosal he behoves to be a narrow bone lying behind the quadrato- 
jugal. In the skulls in the American Museum I cannot satisfy myself 
that an upper fenestra exists. The large triangular bone I believe to be 
the squamosal, and a small bone lying below the squamosal and on the 
quadrate I believe to be the quadrato-jugal. There is some evidence of a 
small fenestra between the squamosal and the quadrato-jugal, though in 
none of the specimens is this region perfectly preserved. There is not 
improbably a narrow distinct element behind the squamosal, and if it be 
really distinct it will correspond to the little bone found in the similar 
region in Procolophon and GaptorMnus (Pariotichus), and which has been 
called epiotic or supra-temporal, but which perhaps might preferably be 
called post-temporal. 
If my interpretation of the temporal region be correct, it follows that 
the structure in the Pelycosaurs is essentially similar to that in the 
Therocephalians, differing only in the fact that the latter have lost the 
quadrato-jugal and the post-temporal bones. Whether there are two 
fenestras or only one, it is, I believe, pretty certain that the large opening 
is the homologue of the temporal fossa of the Therocephalians, and even 
