78 AWany Museum Records. 



overlap the jngal quite so much as in the other species. The 

 scjnnmosal, on the other hand, certainly passes further forward, 

 and the jugal only forms about a quarter of the lower border of 

 the zygomatic arch. The specimen does not show satisfactorily 

 how much of the postorbital arch is formed by the jugal. 



In Opisthoctenodoti the relations of the jugal and the 

 scjuamosal are almost exactly similar to those in Oudmodon 

 triguiiiceps -. the only difference being that the jugal has here a 

 less developed ascending postorbital process. 



In Dicj/)}od(jn latifrons the jugal differs in its relations very 

 considerably from that in Oudenodon. When the skull is viewed 

 from the side, only two small parts of the jugal can be seen, the 

 one in the lower and anterior angle of the orbit, the other in the 

 lower and posterior angle. Elsewhere it is completely hidden by 

 the maxillary, the squamosal and the postorbital bones. The 

 scpiamosal passes forwai-d almost to a level with the front of the 

 orbit, and has a large articulation with the postorbital above and 

 with the maxillary below. The jugal is probably not very much 

 smaller than in Oudenodon truncatus. It forms most of the inner 

 side of the suborl)ital arch and sends a process up behind the post 

 orbital bone. It also forms the inner wall of the anterior part of 

 the zygomatic arch. The posterior part of the maxillary is of 

 large sixe, and forms almost the whole of the lower border of the 

 suborbital arch. In the restoration given by Seeley (-) of the side 

 view of the skull of Dicynodon the maxillary is showai as forming 

 a part of the zygomatic arch. In D. latifrons it does not reach 

 back quite as far as the posterior mai-gin of the orbit. 



In a small Dicynodon skull about 3^ inches in length, and 

 probably lielonging to a new species, the relations of the bones are 

 practically similar to those seen in the smaller Oudenodons. The 

 anterior part of the scjuamosal, however, is here more strongly 

 developed. 



In Lyslrosaarus the jugal is largely hidden by the maxillary 

 and the squamosal, almost exactly as in Dicynodon latifnms. It 

 forms the whole of the lower border of the orbit, sends up a 

 small delicate process behind the postorbital, and has a larger 

 posterior process l)elow and behind the squamosal. The anterior 

 part of the squamosal is well developed and extends forw\ard 

 almost to the level of the front of the orbit, and articulates witii 

 the maxillary. 



It will be seen that in all the above types the structure of the 

 jugal varies very little, and that the diflEerent appearances pre- 



