South African Fossil Reptiles and Amphibia. 189 



The prevomer forms part of the anterior median bar and lies 

 between the palatine process of the premaxillae and the anterior 

 portions of the pterygoids. In shape it is cruciform, the transverse 

 arms forming with the palatines a bar separating two vacuities in 

 the anterior part of the palate. Posteriorly it unites with the 

 pterygoid. In cross-section just behind the transverse portion 

 the prevomer is seen to be a triangular bone with its apex above, 

 and undivided by any median suture. Superiorly it supports 

 a thin plate of bone which has been crushed in the specimen. This 

 thin plate passes back to meet the upper portion of the pterygoids 

 the exact method of articulation is not perceptible. 



There are no palatal teeth, nor does the palatal surface of the 

 maxilla carry any molars. 



The palate shows many features of interest, and is seen to differ 

 considerably from any described South African form. In the 

 first place there are the two anterior vacuities to be accounted 

 for. Fortunately it has been possible to develop the type specimen 

 In nly completely, and the main structure can be ascertained. 

 The median bar lies considerably above the level of the dentigerous 

 border of the premaxilla and the palatal portion of the maxilla ; 

 in fact, the front of the palate is highly vaulted. The inner border 

 of the anterior vacuity is formed by the premaxilla and the pre- 

 vomer the median bar. On the palatal surface half of this bar 

 is formed by the prevomer ; but on the nearly vertical side, of the 

 bar the premaxilla plays by far the major part. The side- wall 

 of the bar does not ascend to the roof of the skull, but stops abruptly 

 about half-way between the palate and the under side of the roof. 

 The front border of the cavity is formed by the premaxilla, the 

 outer border by the maxilla, the posterior border by the palatine 

 and prevomer, and it is roofed by the cranial bones of the region 

 of the nostril. Into this cavity the outer foramen, seen lying 

 external to the nostril in outer view, leads directly. 



The posterior cavity is bounded by the transverse bar anteriorly, 

 bv the palatine laterally, and the pterygoid and prevomer medially. 

 A vertical section fortunately obtainable shows that the two 

 cavities anterior and posterior are connected with the external 

 nares. The "transverse bar' has its upper surface sloping 

 downwards and backwards, forming \vhat seems to be the floor 

 of the narial passage, leading one to conjecture that the posterior 

 vacuities are the internal nares. The anterior cavity must then 

 be the anterior palatine foramen (foramen incisivum). Although 



