Reptilian Lower Jaios. 575 



modified occurs in all known types of Thevapsids, and it 

 occurs in no other reptiles whatever. 



The splenial is a long narrow strip of bone lyintr on the 

 inner side of the dentarj, but not entering the symphysis. 

 Tlie coronoid has never been figured, but is said to be a 

 narrow slip of bone, presumably lying inside the dentary 

 over the splenial. 



Anomodontia. 



The structure of tlie lower jaw of B'lcynodon has been 

 described by Owen and Broom. Seeley has described the 

 lower jaw of Endothiodon, which has an essentially identical 

 structure. None of these descriptions is complete or altogether 

 accurate. 



The present description is founded on a beautifully pre- 

 served lower jaw of a new species of Dicynodon {Owlenodoii-=s. 

 female Dicynodoii) from tlie Gisticephalus-7,one of Kuils 

 Poort, Beaufort West District, collected by tlie autlior. 

 Several other jaws in the British Museum have been used 

 for comparison, the sutures between the bones of the back of 

 the jaw being best shown in a fragmentary jaw of Kanne- 

 meyeria* collected by the author at Winnaarsbaaken, 

 Burghersdorp District. 



Tlie dentary is a ver}- powerful bone, uniting with its fellow 

 in a median symphysis which completely closes even in quite 

 young individuals. The posterior part of the bone is pro- 

 duced into two processes, the upper of which is split vertically 

 into an inner and an outer plate, leaving between them a 

 deep groove which receives the anterior ends of the surangular 

 and angular. 



The lower process, which is separated from the upper by a 

 deep notch, forms only the outer surface of the same groove, 

 the inner side being provided by the splenial. 



The splenial is a short bone, meeting its fellow in a very 

 strong fused symphysis. Behind the region of the symphysis 

 the bone is a thin plate, separated from the dentary by the 

 groove already referred to, which in this region receives the 

 angular and prearticular. 



The coronoid is a thin slip of bone lying on the inner face 

 of the dentary, separated from it and the splenial by very 



* Eannemeyeria is a genus founded by H. G. Seeley in 1908 on an 

 imperfect skull of Dicynodon simocephalus, Weithofer. The genus is 

 easily distinguished from Dicyw>doii, and I know three species belonging 

 to it. The lower jaw does not differ from that of Dicynodon. 



39* 



