90 Transactions of the South African Philosophical Society. 



In the Stegocephalia the carpus is usually but imperfectly ossified. 

 In Eryops, however, it is well ossified, and fortunately a well-preserved 

 specimen is known (3). As preserved there are four bones in the 

 proximal row, five in the distal, and two other elements in the centre. 

 By Cope the four proximal bones are believed to be Eadiale, Centrale, 

 Intermedium, and Ulnare. By Emery (4) they are looked upon as 

 the Eadiale, Paracentral, Intermedium, and Ulnare. While it is 

 difficult for one who has only the figures to go by to give a very 

 decided opinion, I should like to suggest that the four proximal 

 elements are probably homologous with the four proximal elements 

 found in the carpi of most primitive reptiles and well seen in 

 Sphenodon, viz., Eadiale, Intermedium, Ulnare, and Pisiform. The 

 two central elements are undoubtedly centralia 1 and 2, while the 

 five distal elements are as certainly carpalia 1-5. The carpus of 

 Eryops would thus seem to agree closely with that of Sphenodon, 

 and no doubt represents a slight specialisation of the primitive 

 form from which the carpi of all the higher animals have been 

 derived. 



It is probable that in early Permian or late Carboniferous times 

 some member of the Stegocephalia gave rise to the Cotylosauria. 

 This order, though of the greatest interest as containing most pro- 

 bably the ancestors of all the later reptiles, both of the Synapsidan 

 and Diapsidan groups, is at present only imperfectly known. An 

 imperfect carpus of Pariotichus has been described (5), but as the 

 elements were not found in position it is difficult to place much 

 reliance on it. The carpus in Pareiasaurus has not been described, 

 but Huene (6) has recently figured the fairly well-preserved carpus 

 of the allied genus Sclerosaurus. In his Taf. I. he indicates four 

 elements as carpalia 1-4, and this identification seems probably 

 correct. Proximal to C 3 and C 4, and situated immediately distal 

 to the Ulna, is another element, almost certainly the Ulnare. In 

 Taf. II. what is evidently the counterpart of this Ulnare is marked 

 " Pisiform," and a more proximal bone is marked " Ulnare." What 

 is regarded as Ulnare in Taf. II. seems to me to be a portion of the 

 Ulna. The element between the Eadius and Ulna, and which 

 Huene regards as the Eadiale, I should incline to regard as the 

 Intermedium. The element marked C 3 in Taf. II. does not appear 

 to be the same as C 3 in Taf. I., and is in my opinion the centrale. 

 It is thus probable that the Cotylosaurian carpus consisted of four 

 proximal elements, a centrale, and four distal elements. While the 

 specimen of Sclerosaurus practically proves these elements to have 

 been present, it does not disprove the presence of a second centrale, 

 and as many of the descendants of the Cotylosaurus retain two 



