238 Mr. R. Broom on the 



of the symphysis. The surangular forms the upper half of 

 the back of the jaw as indicated in the figure. Von Huene is, 

 I think, in error in regarding the large opening in the side 

 of the jaw in specimen 4716 as natural. Only a small part 

 is, I believe, a natural opening, the rest due to faulty pre- 

 paration. In other specimens the lateral opening is quite 

 small, as indicated in the figure. 1 find no evidence of a 

 coronoid element. Inside the jaw is a large prearticular. 

 The articular is evidently quite small, and possibly carti- 

 laginous. 



Though the structure of the skull of Lysorophus may now 

 be said to be pretty well known, there is still some little 

 doubt as to the affinities. Lysorophus agrees closely with 

 no known animal, recent, or extinct. With Williston 1 agree 

 in holding that Lysorophus is not a reptile. AH known 

 reptiles are either Cotylosaurs or are manifestly derived from 

 Cotylosaurian ancestors, but Lysorophus is neither a Cotylo- 

 saur nor can it have been derived from a Cotylosaur. The 

 supposed reptilian resemblances are entirely fallacious. 

 Von Huene in his recent paper, though correctly figuring 

 and describing the occipital condyle, says : fl this condyle is 

 intermediate between the true reptilian condyle and the 

 true amphibian condyle .... The structure of 'the condyle 

 shows a great resemblance to that of the Theromorphs and 

 of Turtles/' In Theromorphs and Turtles the condyle is a 

 tripartite condyle, of which the upper two-thirds are formed 

 by the exoccipitals and the lower third by the basioccipital. 

 Iu most Chelonians and Theromorphs the exoccipitals come 

 close together, and the basioccipital is squeezed out from 

 the foramen magnum. In all generalised forms the condyle 

 is a projecting rounded structure which articulates with the 

 arches of the atlas and with the intercentrum. In Lyso- 

 rophus the whole articulation is with the centrum of the 

 atlas, which fits close into the broad hollowed out surface 

 formed by the basi- and exoccipitals. The presence of a 

 large articular surface on the basioccipital seems at first 

 sight to be a non-Amphibian character, but, as Watson has 

 recently pointed out, this is the primitive Amphibian 

 condition. The early Stegocephalians of the Lower Car- 

 boniferous, such as Pteroplax, have the basioccipital forming 

 practically the whole of the articulation, the exoccipitals 

 only very gradually in later forms taking the place of the 

 basioccipital. So that, so far from the occipital condyle of 

 Lysorophus indicating any reptilian affinities, it is really in a 

 more primitive condition than is found in any other Permian 

 or later Amphibian. 



