238 Mr. R. Broom on the 



of the sympliysis, Tlie siiranguhir forms the upper half of 

 the ba*k of the jaw as indicated in tlie figure. Von Hueneis, 

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

 of the jaw in specimen 471(5 as natural. Only a small part 

 is, 1 helieve, 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 

 eoronoid element. Inside the jaw is a large [)rearticular. 

 Tiie articular is evidently quite small, and possibly carti- 

 laginous. 



Though the structure of the skull of Lysorophus may now 

 -be said to l)e pretty well known, there is still some little 

 donbt as to the affinities. Lysorophus agrees closely with 

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

 in holding that Lysuropkus is not a reptile. All known 

 reptiles are either Cotylosaurs or are manifestly derived from 

 Cotylosaurian ancestors, but Lysuruphus is neither a Cotylo- 

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

 sup[)osed reptilian resemblances are entirely fallacious. 

 Won Hnene in his recent j)aper, though correctly figuring 

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

 intermediate between the true reptilian condyle and the 

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

 shows a gieat resemblance to that of the Theromorphs and 

 of Turtles." Jn Tlieroiiiorphs and Turtles the c(mdyle is a 

 tripartite condyle, of which the ui)|)er two-thirds are formed 

 l)y the exoccipitals and the lower third by the basioccipital. 

 In most Chelonians and TherouKn-plis the exoccipitals come 

 close together, and the basi<)ccij)ital 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 iiitercentrum. In Lyso- 

 ro])lius the whole articulation is with the centrum of the 

 atlas, Avhicli 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-Am])hil)ian 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 basi 'ccipital forming 

 practically the whole of the articulation, the exoccipitals 

 only very gradually in later forms taking tlie 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. 



