STRUCTURE OF THE REPTILIAN TARSUS. 



151 



reptile allied to Sphenodon. But a few years ago Williston came 

 to the conclusion that it was a Pelycosaur or a near ally, and 

 Watson holds a similar opinion, stating that " it now seems almost 

 certain that Palceohatteria is really a Therapsid.'' It is difficult 

 for one who has no chance of seeing the actual types to know 

 which authorities he ought to follow, and though the tendency is 

 always to follow the latest, I personally do not feel at all satisfied 

 that Williston and Watson are right in this matter. The skull 

 as restored by Jaekel— and his restoration seems to me the best 

 we have vet had— is very unlike that of any Pelycosaur or 

 Therapsid : the shoulder-girdle is entirely unlike and the pelvis 

 is only a little like. The humerus also has only a very slight 

 resemblance to that of a Pelycosaur or Therapsid. Fortunately 

 the tarsus is fairly well preserved, and, as figured by Jaekel, has 

 two large proximal elements, which he considers, as also I do, to 

 be the fibulare and intermedium (text-fig. 13). The only other 

 ossified elements are the five distal tarsals. Possibly there has 

 been a cartilaginious tibiale. If so, the only difference between 



Text-figure 16. 



Text-figure 17. 



Text-figure 18. 



Text-lijr. 16. — The right tarsus and metatarsus of Broomia perplexa Watson. 



A primitive Permian Sauropsidan. The remains as found. Left reversed. 



After Watson. 

 Text-fig. 17. — The tarsus and metatarsus of Broomia as restored by Watson. 

 Text-fig. 18.— The tarsus and metatarsus of Broomia as restored by the writer. 



the tarsus of Palceohatteria and that of Broomia would be that 

 the former had lost the small centrale. 



On the evidence of the published figures of Palceohatteria I am 

 inclined to regard it is a primitive Diapsid reptile, a little more 

 advanced than Broomia and a little more primitive than Youngina. 



Youngina is the only known Permian Diapsid in which the 

 tarsus is fully ossified and almost perfectly preserved (text- 

 figs. 19 & 20). In this tarsus there are two large proximal 

 elements — the fibulare and intermedium with the tarsal foramen 

 between them, five distal tarsalia, and a large element situated 

 between the intermedium and the first, second, and third tarsalia, 

 which I believe to be the tibiale. 



The fibulare is a flat bone which has a very distinct heel 

 process. The intermedium is very large and with a large 



