Beptilian Lower Jaws. 



585 



Upper Permian age from the Orange Free State, South 

 Africa ; the excellent series of specimens in tlie British 

 Museum show all points of the structure of the mandible with 

 great clearness, except the upper edge, which in all cases is 

 obscured by the skull. 



The dentary is a long shallow bone meeting its fellow in a 

 loose suture and extending backwards on the outside of the 

 jaw until it meets the angular and surangular : it never 

 reaches the lower border of the mandible. 



Fi-. 6. 



A. Ceft ramus of lower jaw of Bothriceps, inner aspect. B. Right 

 ramus of the same jaw, outer aspect. Teeth omitted, x 1. 



The splenial is the bone figured by Branson in Annscliisma 

 and Eryops without determination and with some doubt. It 

 was clearly figured by Smith Woodward in Lahyrinthodon 

 leptognathus, and called infra-dentary by analogy with the 

 bones of that name in the Crossopterygian jaw ; the homology 

 implied by this nomenclature is no doubt correct. 



In JJothriceps it is a small element with a large symphysis, 

 forming the lower border of the anterior part of the jaw; 

 posteriorly it meets and overlaps the angular. 



Dr. A. S. Woodward, in his account of the Lahyrinthodon 

 jaw, described a little slit on the inside of the jaw lying on 

 each side of the symphysis, bounded by the " infra-dentary " 

 below and the dentary above. These little vacuities also 

 occur in the type specimens of Rhinesuchu.'i oioeni (Lydd.) and 

 Rhytidosteus africanus, Owen, and no doubt generally in the 

 group. They correspond exactly with the similarly placed 

 openings in Pariasaurus described above, and are clearly 

 shown in Williston's figure of Casea and Williston and Case 

 on Diadectes lentus. 



