STRUCTURE OP THE REPTILIAN TARSUS. 



153 



is almost typically Therapsid or even mammal-like. A few years 

 ago I figured a well-preserved tarsus under the name Gcdesphi/rus 

 capensis, believing it to be a Dromasaurian. The few points in 

 which it differs from the Dromasaurians are points in which it 

 agrees with Youngina, so that it is much more likely that it 

 is an Eosuchian. 



Another very interesting tarsus is that of the South African 

 Upper Triassic Rhynchosaurian, Howesia browni (text-fig. 21). 

 The tarsus is almost perfectly preserved though doubled over, and 

 the restoration I give is probably nearly correct. There is a 

 large fibulare with a heel process, a large intermedium, and a 

 smaller tibiale. There are four distals, and the fifth metatarsal 

 has the Sp henodon-\ ike specialization. 



The tarsus of the adult Sphenodon is well known, and Howes 

 and Swinnerton have given us something of the embryonic 



Test-figure 21. 



I I ^ III 



Text-figure 23. 



Text-fig. 21. — Right tarsus and metatarsus of Howesia broivni Broom ; a Triassic 

 Rhynchosaurian. 



Text-tig:. 22. — Right tarsus and metatarsus of an embryo of Sphenodon punetatus 

 Gray. The embryo is of Dendy's stage R. Ossification has commenced in 

 the metatarsals. Though the proximal tarsal cartilaginous mass shows no 

 clear evidence of its nature at this stage, earlier embryos show that it is 

 composed of three elements, and I think only three. 



Text-fig. 23. — Right tarsus and metatarsus of an embryo of Testudo sp. The 

 embryo is of the stage where chondrification is well advanced, but where 

 ossification has scarcely begun. The very marked difference between this 

 tarsus and that of the Sphenodon embryo is of interest. 



condition. Only those who have studied developing cartilage 

 and precartilage know the difficulties of this mode of research. 

 At times Ave get remarkable results, but too often they are 

 inconclusive. I give a figure (text-fig. 22) of the tarsus in a 

 young embryo of Sphenodon, which I was able to examine through 

 the kindness of Prof. Dendy. Though ossification of the meta- 

 tarsals is just commencing at this stage, there is no clear evidence 

 of the composite nature of the large proximal element. Howes 

 and Swinnerton showed that there was evidence at an earlier stage 



