Investigations in South African Fossil Ecptilia and Amphibia. 87 



pair of fused prevomers, and Watson has recently mentioned that in 

 the type skull of Arctops the bone seems to be actually double when 

 seen in section on the anterior end of the specimen. As a contribu- 

 tion to our knowledge on this subject I have examined skulls of 

 three Gorgonopsians from different zones, viz. Galesiiclius gracilis 

 from the Parciasaurus zone, a snout of Goryonops sp. (S.A.M. Cat. 

 No. 3038) from the Endotliiodon zone of Beaufort West, and 

 Scymnognatlius scrratidens from the Cistecephalus zone of Dunedin, 

 Beaufort West. All these skulls show a cross- section through the 

 vomer. The bone is fairly similar in all three cases with regard to 

 the ventral surface, but the dorsal surface shows some variation, 

 best seen and understood by reference to the figures. 



1. Cross-section through vomer of Galcsuchus gracilis through canine. 



2. Cross-section through vomer of Goryonop* sp. immediately anterior to canine. 



3. Cross-section through vomer of Scymnognathus serratidcns through canine. 



All the figures x 3. 



There is seen on the dorsal surface a progressive reduction of the 

 median ridge, and a tendency for the two grooves to become one. 

 None of the specimens show any signs of a median suture. 



The front of the palate is considerably vaulted, the plane of the 

 premaxilla and "vomer" being above that of the palatine and 

 maxilla, whose inner portions rise vertically at right angles to the 

 outer portions. 



The palatines approximate to each other to form the beginning of 

 a secondary palate considerably below the primary. The palatine is 

 a large bone passing forward almost to the back of the canine. On 

 its posterior and inner portion it carries a few strong, well-developed 

 teeth. 



The pterygoid has a very powerful descending process, deepest at 

 the side of the mandible, and rising to the level of the palatine where 

 it meets its neighbour. The maximum depth of this process is 

 60 mm. and the distance between the two extremities 110 mm. In 



