CLASSIFICATION Ojy THE THERIODONTlA. 93 



It articulates with the nasal posteriorly, with the maxilla in the 

 middle, there being apparently no septom axillary foramen, and 

 with 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 whole struchire is like that of the Tapinocephaloid 

 Jlormosaurus, 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 Gorgonopsids 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 baT. The difficulty is not, however, an insuperable 

 one. 



The relation of the Dicynodonts to other Anomodonts is a 

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

 which can be more satisfactorily discussed now that many details 

 of Gorgonopsid structure are known. 



The characteristic features of all Dicynodonts are : — 



1. The occipital 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 the end of a long tube com- 



municating with the vestibule. 



4. The temporal fossa? are very large. 



5. The face is short. 



6. The premaxillpe 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 roof to the depressed 



median pa.rt of the palate. 



9. There ai-e no definite pterygoid flanges. 



10. There is an interpterygoid vacuity reaching back to the 



basipterygoid process and forward to the prevomei-. 



11. Both quadrate and quadrato-jugal form the articular 



condyle for the lower jaw. 



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



zygomatic part rising from the upper part of a. flat body, 

 the lower part of whose front face is covered by the 

 quadrate and quadrato-jugal. 



13. The dentaries are fused and extremely massive. 



