30 Annals of the South African Museum. 



jaw. A considerable part of its inner surface is covered by the sur- 

 angular, a large part by the prearticular, and a small part by the 

 coronoid. The bone is divided on its lower aspect by a deep groove, 

 as in the Pelycosaurs. 



The surangular resembles that bone in AnomodonU and Thero- 

 cephalians. 



The prearticular is a long slender splint bone. Posteriorly it 

 clasps the articular, and in front lies mainly on the angular, and 

 also articulates with the dentary, the coronoid, and the splenial. 

 Anteriorly it reaches to the molar region. 



The articular is a short strong bone. It is supported by the 

 angular, the surangular, and the prearticular. 



VERTEBRAE. 



The proatlas is a well-developed paired element. Each half is 

 irregularly rhomboidal. It articulates with the atlas. 



The atlas is formed as in Pelycosaurs, Dinocephalians, and 

 Anomodonts a pair of upper arches and a lower centrum which 

 forms the odontoid process of the axis. Each half of the arch has 

 a small zygapophysis for articulation with the axis and a transverse 

 process which supports the atlantal rib. 



The body of the axis is 38 mm. long and 30 mm. broad. The 

 width across the posterior zygapophyses is 38 mm. The neural 

 spine is elongated anteriorly, diminishing in height in the same 

 direction. Its greatest length is 56 mm. and its greatest height 

 40 mm. 



There are four other cervical vertebrae preserved, similar to each 

 other and characterised by a short, rounded body, a long transverse 

 process which forms the articular surface for a single-headed rib, 

 and a low dorsal spine. The third of these vertebrae, which is 

 typical, has the following measurements : Length of body, 29 mm. ; 

 greatest width of body, 37 mm. ; total height, 62 mm. ; height of 

 spine, 11 mm. ; width across transverse processes, 85 mm. ; width 

 across postzygapophyses, 29 mm. 



SHOULDER GIRDLE. 



Both right and left sides of the shoulder girdle are present, the 

 only parts missing being the right clavicle, part of the left coracoid, 

 and the distal end of the interclavicle. The sutures between the 

 coracoids and precoracoids are almost obliterated, but there seems 

 no doubt that the usual three elements are present, and that the 



