South African Fossil Reptiles find Amphibia. 171 



Neither ischium is complete, but the bone is greatly produced back- 

 wards. The pubis is not seen. 



The femur is 95 mm. loug, has a narrow proximal width of 40 mm., 

 and a distal width of 31 mm. The shaft has a minimum width of 

 16 mm. The median coudyle is somewhat smaller than the lateral, 

 and the medial surface of the bone is produced lower than the lateral. 

 The groove between the condyles on the posterior face is a little deeper 

 than that on the anterior. 



Of the lower part of the limb only the proximal half is preserved. 

 The tibia has a strongly expanded end. The fibula is a slender bone 

 expanded proximally. 



This form may be considered as a link between Dicynodon and 

 Lystrosaurus, approaching the latter rather closely. It has close 

 affinities with the form from Harrismith described by Broom as 

 Dicynodon strigops, but is at least specifically distinct in the fact that 

 the plane of the snout is at right angles to the froiito-parietal plane 

 and not inclined at 45. Moreover, the anterior border of the orbit is 

 rounded and not angular. These differences I am inclined to consider 

 specific and thus place Bi'oom's species in this new genus under the 

 name Prolystrosaurus strigops (Broom). 



It is possible that the bending down of the snout and lengthening 

 of the premaxilla and maxilla which must have, taken place in the 

 evolution of Lystrosaurus from the earlier Auomodonts is foreshadowed 

 in such a form as Dicynodon testudirostris from the Cisteceplialus zone. 

 At the same time as the lengthening of the prenasal portion of the 

 snout took place there was a broadening of the frontal region and a 

 shortening of the temporal openings. In these features Prolystro- 

 saurus agrees with Lystrosaurus ; and the discovery of further forms 

 from the upper part of the Cistecephalus zone may enable us to trace 

 out gradual changes between D. testudirostris or some similar form and 

 Lystrosaurus through Prolystrosaurus. 



Type. Skull and'lower jaw. (S.A. Mus. Cat. No. 3715.) 



Go-type. Skull, lower jaw, and nearly complete skeleton (331</). 



Locality. Loskop, Natal. 



Horizon. Middle Beaufort Beds. (Lystrosaurus zone.) 



PROLYSTEOSAURUS STRIGOPS (Br.), 



1913. Broom, Dicynodon strigops. Eec. Albany Mus., ii, 5, p. 400. 

 1915. Broom, Dicynodon strigops. Bull. Amer. Mus. Nat. Hist., xxv, 

 2, p. 140 ; fig. 29. 



Skull rather small. Skull unusually flat, orbits directed more 



