1056 



DR. R. BROOM OX THE ORIGIN 



[Dec. 10, 



groups does not throw much light on their affinities, but from 

 the study of the carpus some interesting facts are obtained. 



Text-fig. 246. 





C D 



Carpiis of SpJienodon and of Mammal-like Reptiles. 



A. Sphenodon punctattis (after 



Howes and Swinnerton). 



B. Galechirus scJioltzi. 



C. Oudenodon trigoniceps. 



D. Galesuclitis hroivni. 



el, c2, centralia ; i, intermedium ; p, pisiform ; B, radius ; r, radiale ; 77, ulna; 

 u, ulnare ; 1, 2, 3, 4, 5, carpalia ; I, II, III, IV, V, metacarpals. 



In. the case of the fossil carpi the elements are figured exactly as found. 

 In Galechirus and Oudenodon there is evidently a slight lateral displacement. 



The carpus is practically unknown in any Ootylosaurian. Case 

 has endeavoured to restoie that of Pariotichus (20), but too many 

 points are left in doubt to make it advisable to take it at present 

 into consideration. Fortunately the carpus is well known in the 

 two very primitive Diapsidan genera Dimetrodon (21) and Pro- 

 GolopJion (22), as well as in the pre-Cotylosaurian genus Eryops. 

 In all three genera the carpus is so essentially similar, and so 

 like that of Sphenodon, that we may feel pretty sure the Ootylo- 

 saurian carpus was also of the Sjihenodon-ty^Q. 



In Dimetrodon, as shown by Case (21), there is a large radiale 

 and ulnare, with a smaller intermedium between two well-developed 

 centralia, of which the inner is the larger, and a fair-sized 

 pisiform. In the distal row are five carpalia, of which the second 

 is the largest. 



In Procolophon (22), as I showed some time ago, the carpus 



