CLASSIFICATION Of THE THKRIOUONTlA. 93 



it iii'ticulates with the nasal posteriorly, with the maxilla in the 

 iniddle, there being apparently no septomaxillary foramen, and 

 witli the premaxilla in front. 



The palatine extends forward to the middle of the canine 

 tooth, forming the greater part of the outer wall of the long- 

 narrow posterior nares; at the hinder end of the opening it has a 

 suture with the prevomer, which appears to form the whole 

 inner border of the nostril. 



The prevomers are unfused, each provided with a high, thin 

 dorsal ridge, similar flanges from the pterygoids passing between 

 and separating those of the prevomers. 



The wliole structure is like that of the Tapinocephaloid 

 Jloriiiosaurus, and especially like that of the detached nose which 

 seems to belong to Lamiasaurus. 



The structure of these palates raises doubts as to the forma- 

 tion of the internarial bar in Gorgoiiopsids by the fusion of a 

 pair of prevomers, because in the Deinocephalia the pterygoids 

 separate the posterior ends of the prevomers, whilst in Gorgo- 

 nopsids they clasp the outer sides of the posterior ends of the 

 internarial bar. The difficulty is not, however, an insujierable 

 one. 



The relation of the Dicynodonts to other Anomodouts is a 

 subject on which there has been much difference of opinion, but 

 which can be more satisfa,ctorily discussed now that many details 

 of Gorgonopsid structure are known. 



The characteristic features of all Dicj'nodonts ai'e : — 



1. The ocLupital condyle is triple, the exoccipitals forming 



its upper parts. 



2. The supraoccipital is only slightly drawn forward to 



form side-walls to the brain-case. 



3. The fenestra ovalis lies at tiie end of a long tube com- 



municating with the vestibule. 



4. The temporal fossse are very lai'ge. 



5. The face is short. 



6. The pi-emaxillje are edentulous and the maxilla is carried 



out laterally to the molar teeth, if any be present, and 

 its margin is a sharp ridge covered by a horny sheath. 



7. There is a rudimentary secondary palate. 



8. The prevomers are fused, forming a I'oof to the depressed 



median part of the palate. 



9. There are no definite pterygoid flanges. 



10. There is an interpterygoid vacuity reaching back to the 



basipterygoid process and forward to the prevomer. 



11. Botli quadrate and quadrato-jugal form tlie articular 



condyle for tlie lower jaw. 



12. The squamosal is of characteristic shape with a wide flat 



zygomatic pai-t rising from the upper pai't of a Hat body, 

 the lower part of whose front face is covered by the 

 quadrate and quadiato-jugal. 



13. The dentaries are fused and extremely massive. 



