172 



THE OSTEOLOGY OF THE REPTILES 



present. In Procolophon only, of the Cotylosauria, is this centrale 

 absent, as is also affirmed of the radiale. Throughout the Thero- 

 morpha, as known in numerous forms, the carpus is primitively com- 

 plete, save that the first centrale and fifth carpale remained cartilagi- 

 nous in one known genus, Varanops. 



^^lJb 



Fig. 138. Limbs: A, Theriodesmus (Therocephalia), front leg, dorsal side (rearranged from 

 Seeley). One half natural size. B, Scymnognathus (Therocephalia), front foot. After Broom. 

 One third natural size. C, Protorosaurus (Protorosauria), front leg. After von Meyer. One 

 half natural size. D, hind leg of same. E, F, Araeoscelis (Protorosauria), part of tarsus, 

 F probably immature. Nine eighths natural size. G, Sceloporus (Lacertilia). Enlarged. 



Among the reptiles collectively known as the Therapsida, the car- 

 pus is ill known. In Galechirus of the Dromasauria (Fig. 137 a) as 

 figured by Broom, the primitive structure is retained, as it also is in 

 Dicynodon and its allies of the Anomodontia. The carpus of Scymno- 

 gnathus of the Theriodontia, as figured by the same writer (Fig. 138 b) 

 has a small intermedium, and the fifth carpale is represented as fused 

 with the fourth, an error. A small element found near the first car- 

 pale was referred to a possible prepollex, or a radial sesamoid. Among 



